After loosing my RC-3 a couple of months ago, I decided to replace it with a STS-3. The STS-3 is a very competent knife and the two are very comparable. In practical work, the differences in the handle are negligible, and both can be used well for long periods of time, but the RC-3 seemed to provide a better grip when wet (I'm working from memory, I don't have both knives to compare side by side). I like the thicker blade on the STS-3 and didn't find it to be a disadvantage relatively to the thinner RC-3 blade as far as normal camping and bushcrafting tasks go. The tip of the STS-3 also seems to be a better driller. But all the above differences are really very small. The only significant difference is the steel: for my applications the stainless offers significant advantages, because most of my trips involve rivers and very wet environments. I found that chopping and light batoning was not a problem with the 154CM. The edge remains sharper longer, too.
I agree with the comments about how poor the kydex sheeth is. I replaced it with an aftermarket leather sheeth.
The bottom line is that I found both knives to be very similar, and that in practice the type of steel is the main distinguishing characteristic. The STS-3 is a more expensive knife, too, and I imagine that for many applications it will be worth the difference in price. For me, after having spent the extra cash in the new sheath, I must say that the price difference wasn't worth it, even if I like the STS-3 a little bit better overall.
