I've had both of the CH pedal types, the narrow, and the REALLY narrow, as well as the older Saiteks.
http://www.saitek.com/uk/prod/compedals.htmlThese are the newer Saitek's I bought with my Warthog setup (yes, I'm one of 'those' guys who bought those peds with that HOTAS).
I've never had the chance to try the SIMpeds, in fact I've never seen a set, and I'm going to get a hold of some asap for comparison, I've ordered a set of the F16USB pedals. That said, the new Saitek combat peds are a huge leap forward from the older saitek pedals and the CH ones in terms of materials and workmanship that they are worth the extra 100 dollars and then some. They do have a larger footprint then the other types of pedals, so be warned if you have a small desk or space you are working in.