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.
IF you don't feel like the wait time or ordering overseas for the SIMPEDS, which are around 400$ Canadian for the ones I have on the way, make sure you buy the Saitek Combat Pedals, as they are the by far the best of the 3 or 4 types that are available in North America easily from say amazon or whatever. Ch Pedals, Saitek Pro, the pedals with the Logitech Hotas....NONE of them are even close to half as good as the Combat pedals, at least to me. The are about 75 dollars more on average than the CH/Saitek Pedals, but for that small sum of cash you get a LOT better product. Try them out at best buy or whatever first, and you'll agree with me.