Those numbers (10600 and 10666) refer to peak bandwidth of the ram. Depending on the ram manufacturer, the number is either rounded up or rounded down. They are one in the same. If you are looking to upgrade your ram, search DDR3 1333.
Do you have a link? It might differ in terms of latency/timings. Honestly, the brand of ram is irrelevant for a laptop because you aren't overclocking. It's just a matter of preference. I personally like Corsair ram. G Skill is great. Crucial is very popular. Kingston is using a mixed bag, some people love their ram, some people hate it. Just get whatever is the best price, you won't even tell the difference. Apple doesn't even use the same ram in every machine.
The MBP manual specifies using PC3-10600S. I'm not sure where the 'S' comes from, because I wasn't able to find any memory that matches that spec on Newegg.
Good point. Looks like an issue with the 2010 iMacs. I checked the manuals for those. Just looking at the manual, the memory should be compatible. The manual only specifies PC3-10600 204-pin SODIMMs. So, any person looking at this, seeing a very rating on Newegg would naturally think that this should work with the iMac. That doesn't seem to the case. Universal compatibility isn't really universal, it seems.
I have a new 2011 MBP coming in and I've had the 8GB G.Skill set of memory on order as well. It will be a few days until I know if this memory works with the new MBP.