If you get a new Slim PS3, chances are it will have OFW 3.56 or above. If you get a Fat PS3, firstly it won't be new, secondly it will most likely have a FW lower than 3.55. That is if the previous owner doesn't just connect it online purely for the purpose of making it up-to-date.

In terms of how a PS3 "utilizes" CFW, there's absolutely no difference between the Fat and Slim models. The hardware didn't change much - they just took out the emotion chip, reduced the NAND size, gave the CPU/GPU a die shrink (uses less power, produces less heat) and stuck a bigger HDD in. Oh, and the Slim PS3 doesn't have the memory card reader at the front. Either way, the software for both has always been the same.

The size of the HDD is not a great indication of the FW it has - the manufacture date is what's important. PS3s with 3.56 have been seen for a while now, so I would imagine that by now all the old stock would have been sold and they'll only have the new stock (with 3.56 or even 3.60) to sell.

 

Ok, then an addendum to my post: new PS3s in retail stores (like GameStation and PCWorld) will most likely have 3.56 or above. I can't speak for online stores because they're almost universally just warehouses with marketplace accounts. The point is that reports of PS3s with 3.56 started turning up a while ago and, by now, all older stock should have been sold on.

Basically if you're buying new, the odds are you'll end up with a PS3 with 3.56 or above.

 

i bought a 320GB/little big planet version about 2 months ago & it had 3.41 on it (uk)

 

3.55 or lower is most common on ps3 sold in stores. buy it at a store thats got a return policy, if its got 3.56 or higher return it, say it was a gift and the person already got one and you didn't know about it.