I actually bought a black 3ds XL about 4 weeks ago and it was my first nintendo handheld since the gameboy SP, so I was completely new to the whole DualScreen series.
At first, I really liked it. The size wasn't all too bad. It was somewhat comfortable in my hands but would still cramp after a while. The screen size was pretty nice too.
I somehow found out about the gameboy Micro and my decent into madness with getting a smaller console began. I went insane researching the micro man. I loved the size of that thing. I ended up making a real-scale model of it using paper. I shit you not, I am quite insane.
Here is a picture.
Yeah man, those are tiny little pieces of paper I cut and taped on there. I really wanted to see the size.
Anyways, after making that model I pretty much gave up hope on the micro as it was just way too tiny.
I don't really remember when it was that I thought back to a video I saw that compared 3ds 3ds XL and DS lite. I thought to myself, there was this one console that had a sweet glossy finish
(don't really like gloss) but it looked really sexy and the inside of it was really sexy too. Then I remembered the size was perfect too. Of course I'm talking about the original 3DS.
Man I rushed over to best buy and bought the original 3DS because I knew I had a 45-day extended return policy
(best buy club or something) on my XL and it was only 12 days past the date of purchase.
(oh and yeah they did accept the return no reduction/fee/problems. I returned the XL 2 days after)
Best freakin decision of my life!
The 3DS design is EXCELLENT! --- for me. It's just the perfect size --- again, for me. I just loved it the first second I opened it up. Oh and the picture quality is SO much sharper since the resolution is the exact on the 3DS and XL - it's just the XL streches out on a larger screen. Most people say the XL is fine, but I just go insane comparing the two. Even though the original screen is 90% smaller, the sharper image is just wayyyyy more beautiful ---- to me. Oh hands down, the speaker quality is better on the original xD not important though lol.
What I'm trying to get at is it REALLY depends on the person. There are so many different factors to consider. First you have to determine what your cousin truly cares about.
Screen size? Sharper quality graphics? Portability?
Since you said he is on the go, it seems that the original is a better fit. But is that what concerns him the most? Being able to take it anywhere? What if he actually prefers the larger screen? You could still somewhat fit the XL into your back pocket, it's just a little bit more of a tight fit.
As far as the top screen being scratched by the bottom, I thought I read that about the XL. I actually noticed some strange markings on my XL when opening it up
(from the closed positon, not new from the box duh), but nothing that couldn't be wiped away - but of course I did have screen protectors on both screens.
But with my original 3DS - I have not experienced a single scratch on the screens - before/after opening/closing the lid. I actually just took a look at it and it looks like there are two tabs on the lid, left and right that make contact with the bottom part, so I think those are blocking the top screen from making contact with the bottom screen.
Microfiber cloth will help. I actually had a tablet that had a case on it that was a little too tight when closed and would leave a mark on the screen. I ended up putting a cloth on the screen before closing up the case and it would be perfect with no marks when opening up. So it would be the same in this situation.
As far as the dpad, I just have not had it long enough to comment from personal experience but I have read that it's a little different from the XL. I'm not sure which, but one of them is more 'clickly' than the other. I think it was the XL because the original seems perfect to me.
Quick little tip about gloss and matte finishes - you can always get a DecalGirl skin. All of their skins come with an option of gloss or matte finish. You can even get an originary color skin to match the color of the 3DS if you don't want an actual design or something that stands out - you just want to change from gloss to matte finish or vise versa.
Hope that helps!