I tried the Hexagon demo and liked it but didn't give it much time before the thing expired. But if you've got it already then you'll know whether you like it or not. I have Silo and like it very much. I especially like its speed and the way you can customize the UI and shortcuts pretty much anyway you want (you can even make your own buttons if you want). It has a few things Hexagon doesn't. The Bridge tool is a very quick way to build up volume in a model. And the topology brush has already been mention. I think alot of people assume that this is simply for tidying up topology but it is a very straight forward way of modelling clothes or anything else that has to conform to another model. Anyone buying Silo now won't have to pay for the upgrade to 2.0 which is promised by the end of the year. That will include a UV editor and displacement painting. Silo also has an active community with which the programmers are regular posters. There's also a demo version, so you can try it!