Shouldn't both images be reduced to the physical size of the (in this case PSP) screen for a more proper comparison though? And of course there can be disadvantages as the new iPad shows when games like Nova 3 have to reduce their visual settings to run decently on it. If you'd isolate resolution as its own thing that doesn't affect and isn't affected by other factors, yeah, more is better every single time, but it's hard to do that when it can affect things enough to reinforce coming failures. Any gamer would rather have the most powerful and most successful system ensuring a healthy library for a long time, but when you have to choose one the latter works for most.
Anyway, the 3DS ppi is pretty decent (akin to iPad2 and other similarly modern gadgets iirc?), going for the LL or not is up to one's preference and convenience, options are rarely, if ever, bad anyway. Speaking of the iPad2 I guess an even better and proper comparison would be to view the same 3D scene rendered on an iPad2 in its native resolution and then on the new iPad in its own native resolution. A scene that isn't taxing enough to cause the new iPad's version to need downgrading at least.