3D immersion is definitely a plus, sure. Sweet spot I've heard conflicting reports on, but I have no problem with the OG's sweet spot, I've adjusted to holding it steadily. Quality of screen... my understanding is that the screens are identical, quality-wise? So really it just comes down to size and pixel density. 3DS games have always seemed pretty "HD" to me, due to the nice DPI, I just hate to lose that.
I am lured by the build quality and comfort from largeness, though. But also turned off by how it looks on the outside of the system, and the lack of pocketability. I'm just used to DS redesigns being much easier to want, I guess, and the XL here is giving me a lot of reasons in the Against column. I guess I never bought into the DSiXL either, though. "Bigness" just aint that much of a plus for me in my handhelds. Gimme a 3DS micro, if anything!
Some of my biggest "wants" for 3DS XL are the battery life, larger screens, smooth edges (which look far more comfortable than the standard 3DS's beveled edges,) and the increased DPI for DS games running at 1:1. (I felt let down when I first played DS games on 3DS compared to on DSi.)
So last night I borrowed a DSi XL to play around with, since I don't have access to a 3DS XL and the two units are nearly identical in size and weight. Obviously the DSi XL's DPI is terrible so I ignored that, but the screen size is generally similar I imagine (for the touchscreen at least.) My game of choice was Elite Beat Agents because I wanted to get a feel for stylus-heavy games on a larger screen, and what I found was that the heavier system combined with the larger range of motion required made the game more difficult to play. Afterward I moved on to a little NSMB just to get a feel for the system as it plays without a stylus.
Once I was done there, I set down the DSi XL and grabbed my 3DS to play the same games and compare. The moment I opened my 3DS and had it in my hands, I did a complete 180 and am now about 95% sure I
don't want a 3DS XL. It all came down to comfort. The standard 3DS just felt so much lighter and the smaller size was much more comfortable for me (worth mentioning: I have fairly small hands for a guy.) It just felt "right" in my hands. I then proceeded to play some EBA and NSMB on my 3DS in both stretch mode and 1:1 and found both experiences superior to the DSi XL.
Obviously it all boils down to opinions, as I've heard tons of praise for the DSi XL and now the 3DS XL too. But for me, I felt like a little kid whose hands were far too small for the system I was trying to play (again, this was a DSi XL, not a 3DS XL.) I still want to try a 3DS XL firsthand, but I expect that will only solidify my decision to pass this time.
If you're even remotely on the fence like I was, I suggest trying to get firsthand experience before committing. Especially if you've never used a DSi XL or if you typically prefer smaller handhelds.
On the bright side, if Nintendo comes out with another revision in a year or two that's similar in size to the 3DS/DSi, I'll probably be sold in an instant.
Sorry for the wall of text.