Wow. Lots of great suggestions. This is not going to be easy.
I am thinking Rat Cutlery might be a good intro for me, particularly the RC-6, mentioned above. I guess I would be doing mostly light batoning, to answer bladekillers point-- to be honest, I haven't done much backwoods camping to date, so I am not sure what my needs will be as I get more into it.
Regarding the Rats and the Ka-bars-- as the Rats are about double the price, which I imagine relates to the quality in some fashion: what exactly are the differences? Is it balance, materials/durability, steel type? Would I notice a big difference were I to opt for the Rat instead of one of the ka-bars of a similar size?
Jake Bauer's response to you was quite good here and I concur with what he said. Price point is a very difficult thing to wrap you head around from a beginner's perspective. As mentioned, there is the buck 119 which is a very capable knife at $40 and then the kabar Beckers that give you every bit of knife you need at $60-80. They are as robust and as effective as the higher cost RC-products.
You won't really notice a difference in performance between the RC-6 and say the BK-7. They are both excellent utility blades. The differences between the two are more about little things. The handle material on the RC-6 is mircata compared to a type of plastic on the Becker. Mircata is one of the premiere synthetic handles, arguably the best there is for comfort, grip and ability to withstand any kind of punishment. You can get mircata upgrade scales for the Beckers, however, as a factory spec'ed replacement scales they are not mated to the knife you buy (neither are the plastic ones that come with your knife) and therefore will not fit perfectly like an RC one will.
As mentioned by Jake Bauer, the fit and finish on the RC-knife is flawless. As somebody new to knives, the reality is you might not yet have an eye for picking out little details, like scales not being perfectly even with the tang, indents and tool marks on the blade and spine visible from beneath the coating etc. These traits are mostly cosmetic and bear no impact on the use of the knife. If you really just simply view your knife as a utility tool than get the cheaper Becker. It will perform well.
One difference between the two is the handle on the Beckers is a lot thicker than the RC-handles. Some prefer the Beckers and others prefer the RC-6. The RC-6 scales are much thicker and longer than on the RC-4 (some folks complain that the scales are too small on the RC-4). Personally, I like the RC-6 handle comfort much better than my BK-7. I removed the scales on the BK-7 and came up with different option because I felt they are too thick. Handle comfort is something unique to each person, so what fits my hand may not translate to what fits yours.
The RC-6 sheath is excellent and very well thought out compared to the BK-7 sheath. However, some people really don't like the RC-6 sheaths and the fact that they are meant for clipping to molle webbing, don't come with a belt loop (you use paracord tied between the rivot holds to form a belt loop) and are made of moulded plastic.
Also, asided from batoning, does a much larger size blade impart other advantages? The RC-6 is about 6 1/2 in. Would that be significantly more functional then an RC 3 or 4? Or might there actually be an advantage (besides, of course weight and packability, which certainly counts) in a smaller size?
Batoning is something where size helps but it really is a matter of the wood you process. You can do most things with a 4" knife. If you are willing to make wooden wedges to facilitate your batoning, you can pretty much split any size wood with your 4" blade. However, this requires time and skill and it is much easier to split a piece of wood with a knife whose length extends it past the cross section of the wood. This way you can bang on the tip after the spine has sunk into the wood.
While some folks have recommended even longer knives, like 9"-10" or longer, I personally don't see the value of such very long knives. Sure, they make batoning easy because you have a large amount of knife tip sticking out of the wood to baton, but are you really going to be splitting 8" rounds with a knife? Basically, it amounts to the type of wood you think you are going to be splitting. When I'm splitting the big stuff, I generally have an axe. However, I don't really use the big stuff for making a little camp fire. A lot of folks argue that you don't even need to split wood for campfire prep, you just gather fallen dead wood and break or leverage it apart using trees or your knees etc. Again, it is a matter of the type of wood you are using, the conditions you find yourself in when gathering wood and what nature is providing you. If you car camp frequently and buy your wood e.g. from the camp store, it is usually pre-split into half and quarter rounds. A 6" knife will be all the length you need to pair down one of those pieces for making your kindling.
The one area where long knives, 9" or so, do have a major advantage at is chopping. No 9 or 10" knife will out chop a good axe, but they certainly are much more efficient than chopping with a smaller knife. The BK-7, because of its length, makes a better chopper than the RC-6. In testing the two together, this amounts to 3 or 4 fewer chops to get through a 2" piece of wood. Again, on a performance basis you say one wins, but the reality is that the performance is pretty close. A 9" knife might get you throw in 6-10 fewer chops compared to the 6-7" ones.
The other area where length comes into handy is food prep and kitchen type duties. This seems incredibly unexciting, yet when you think about it, food prep is something where you use your knives the most. If you are cutting onions, potatoes, other veggies or melons, the extra length afforded by a 6" comes in handy.
The disadvantages to carrying a longer blade are weight of carry, the length and real estate it takes up on your belt. In some cases the negative perceptions that other people may come to upon seeing a large blade on your person may also make a difference. The later seems silly when we are talking legal carry options, but the reality is that it is important to many people and even influences my decision frequently on what I carry and where. On this basis, I generally find a 9" blade just too big to comfortably wear on my belt. It slaps your leg while walking and is heavy and awkward.
A 6-7" blade is better but you still know that the knife is there on your hip. One reason I like the RC-6's sheath is that with the paracord loops, it rides tight and high on your belt. This makes it feel like a smaller knife when carrying it by belt. However, the mode of carry does interfere with a pack belt and you might want to consider a dangler attachment to drop the knife down under your pack belt. In that case, I usually just lash the knife to my pack and keep a smaller fixed blade, like the Izula or RC-3, on my person.
Sorry - this was so long winded. Just trying to give you my perspective of camp knives. If I were routinely backpacking, I would definitely go the 4" route.