The reason why it was a direct port to PC was because
a) the community demanded a PC version and the developers made it clear they'd only do a complete copy, no additional work
b) they had never worked with PCs. Zero experience.
The biggest issue people had were the graphics, they were the same as the consoles. Which frankly is not much of an argument as gameplay trumps graphics always. This became irrelevant because on release DSFix was created which vastly improved the graphics/preformance.
It's not because they just spat out a port to make dollars, they had no experience and had no intention of making it for PC. They made the community well aware it'd only be a direct copy prior to release.
Now, the actual difference between the two version is GFWL. Games for Windows Live really fkd the PC release... massive issues trying to co-op, invade, etc. To this day I struggle to do those actions on PC, while it's the opposite on PS3. I also suspect it's due to the difference in players - PC players seem to swap games in and out a lot more than console players. Pretty sure the amount of PC players has dropped off significantly.
Overall, I recommend PC for the awesome graphics. The game is stunning.