The main drawback to most guided sharpening systems is the relatively small stones used; some are much smaller than others (Lansky system, for example). The smaller ones I think were really designed and intended for lighter touch-up & maintenance work, instead of for heavy grinding and rebevelling, though nearly all of them get used for such heavy work. A benchstone always has an advantage in grinding speed for this reason, as it's surface area makes the biggest difference in how fast it removes metal. A typically-sized bench stone will likely cut the working time in half, and maybe down to 1/3 or 1/4 of the time needed with a smaller guided hone. Another advantage of using a larger stone is it's conduciveness to long, smooth sharpening strokes, which usually translates to better results and a cleaner finish on the bevels. There's necessarily a lot of 'back & forth' involved in using smaller stones for heavier grinding work, and that can make it more difficult or awkward to leave a clean-looking finish on the bevels and a clean-cutting apex at the edge. You can stick to only edge-leading passes with the smaller stones, to maintain a clean & even scratch pattern; but that also will be very slow-going during earlier grinding stages. Smaller stones will also wear & clog much faster, because all of that grinding is done with relatively little abrasive stock. All of this is why I suggested using a guided clamp that works well with a bench stone, as it still allows you to take advantage of the larger stone's cutting speed and ease of use.
The Aligner clamp is made to be used with either a bench stone or with guided-rod hones (such the 'Aligner' set or with DMT's DiaFold hones and the 'MagnaGuide' accessory used with them). So, the upside in trying it out is, you can get the clamp with a set, or use it by itself with your bench stones, depending on which sharpening task is being done (touchups or heavier work).
David
I'll give a bit of a counterpoint to this... mostly for the conversation. I do agree that the smaller guided systems like the Lansky have a bit of a struggle with grinding and rebeveling (I remember trying to sharpen some kitchen knives with one that hadn't been done in over 15 years)... but the better guided sharpening systems I mentioned above do a much better job at this. You also get the advantage of "each stroke working", in other words the stone is set at an angle and each stroke removes metal where you want it to. Freehand OTHO, especially when learning how, can actually take longer, regardless of stone size, because there is a bit of "waste" for lack of a better word, in some of the work done. There's also no reason to stick to "only edge-leading passes with the smaller stones, to maintain a clean & even scratch pattern", you can go back and forth especially in the early stages... the final stone you can set the edge/bevel with the grind going in whatever direction you want.
I'll also say (probably my main counterpoint)... I don't really comment on this much, because I didn't spend a lot of time with it, but I often wonder if the DMT Aligner clamp was designed to be used with a bench stone, or if it was more of an afterthought. You can do it, and it does work to some degree, but I found it to be very slow and limiting. A lot of knives didn't seem to fit the scenario... especially ones with much of a belly. It's limited on where you can clamp the blade and get the whole knife to contact the stone, it's hard to match what is already on the knife, so you either have to regrind or sharpen at a higher angle, and I found it to be slow... it just didn't seem designed to me anyway, to work well dragging the plastic clamp across a table with the knife on the stone. I think it would be more trying to do major work with this, than other guided systems. I might suggest it if someone already had the Aligner, and like i said to some degree it works, but not very well IMO... and if one were to go this route, I'd suggest diamond bench stones, because, as OwE said earlier, adding water or oilstones which are often of various thickness, just throws another wrench in the works. Just never seemed to me to be designed with this in mind. If one wanted to use a "guide to learn freehand", I think the Razor Edge Systems clamp that Mahoney mentioned is a better route. Just to be clear, I'm not saying OwE is wrong, this was just my experience and take on it... (feel free to clarify if I'm missing something here)... I just found it such a poor method, that I didn't spend a lot of time with it. (I do think it works well when set up with the rod guided stones).
BTW, I'm not advocating "buy a guided system"... if you want to take the time to learn freehand, it's a great way to sharpen. I spent the last year or so, really concentrating on freehand sharpening over guided sharpening, and while I think guided systems still have some advantages, I'm happy with the edges I'm getting now, and it is less limiting in many respects sharpening freehand vs. sharpening within the confines of a guided device... if you take the time to learn, what OwE says in this area is true.
