AFAIK there are no significant changes to the base models other than the power lift gate. The only person who can decide whether it's worth it is you...many people in this forum do not believe the added weight is worth the added convenience. Personally, I obviously don't have one BUT my wife's Murano does, and she thinks it's an absolute necessity. If your hands are full it's nice to just press the button and have the lift gate rise for you...at the expense of several seconds of wasted time waiting for the lift gate to open and close. I've honestly never tried to swing open or close the gate by hand, so I don't even know if it's possible. You may think that "several" wasted seconds is trivial but it does become an annoyance after a while.
As far as comparing the two models, you have to make sure you're comparing apples to apples. There are several expensive options available on the FX... if both models are similarly equipped, I'd take the 2010 and grind the dealer on price. As far as trying to figure out which options are on each vehicle....well, you're kidding, right? There isn't a window sticker on each vehicle that explicitly lists the options? If not, then you should expect the dealer to explain the option details and advantages (and cost) of each. Make him earn his commission. Once you have all that figured out, then you can make an informed decision.
But like I said, if they're similarly equipped take the 2010, make sure you know what all the incentives are (I recall reading that Infiniti is offering some pretty good cash-back incentives on 2010 models right now), and then grind him on price. You should be able to do much better than the 5K he's offering.