Hi Djmlaw,
Choosing between these two would be like asking me to choose my poison. Neither have good value IMO and there are many better choices.
You can see an analysis of the iComfort models in Post #11 here
Post #10 here has my thoughts on the Tempurpedic lineup.
In essence … the Tempurpedic is a higher quality lineup but significantly overpriced compared with many other choices that are widely available. The iComfort have hit a “sweet spot” in terms of how they feel (they are a nicer feeling memory foam mattress lineup) but the quality of the materials and the design of the mattresses caters more to a “showroom feel” that unfortunately is the basis of how many people choose a mattress than it does to long term satisfaction and durability in daily use.
There is a set of guidelines here that may help you avoid most of the worst choices when you are immersed in the frustrating and confusing world of mattress shopping.
Local factory direct manufacturers or smaller brands sold through better sleep shops are usually far better quality and have lower prices … meaning better value.
If you let me know the city you’re in I’d be happy to see if I know of any better choices in your area.
Phoenix