The + has double flash and cpld, which improves emulator performance somehow (they never would give me a clear answer on exactly what it does), and reduces load times in games (loading the next level off the rom. Not loading roms off the SD)
More threads (what most PC users would call "cores"), more happiness.
As far as I can tell, it actually runs SNES (16-bit) games
MUCH better even on an old 3DSXL. With the New3DSXL you have all the DSTwo+ cores
AND the New3DSXL cores. Which is why the New3DSXL can play SNES VC games. The Old3DSXL cannot. HOWEVER, the O3DSXL can use the DSTwo+ to play SNES games!!! Yay!
Many of the emulators that DSTwo uses allow for you to select how many "threads" to use which can speed up or slow down a game. The DSTwo+ gives you more, while the old is limited to what it had.
More memory (not memory as in mSD memory), more games.
Another reason to buy both a New3DSXL & DSTwo+:
You A9LH the New3DSXL for CIA/3DS games and let the DSTwo+ run all your VirtualConsole games (even the ones they refuse to put on eShop). If you don't understand what I'm talking about, google "BS Zelda" or check out YouTube and search "ClanOfTheGreyWolf" and watch the entire playlist of "16-Bit Gems". There were SNES games that made it to other systems (Genesis, TurboGRFX-16) which were
MUCH better than the SNES versions. BS games... well, you'll see. There's a Zelda game you just can't buy. Need I mention being able to play translated versions of all the NES/SNES/GB/GBC/GBA/etc. Japanese games we'll never see on the American market (Mother). Some made it to EU, but most of EU were US ports. However, sometimes the EU market got what the US didn't from Japan (Gaia Trilogy). Do watch "16-Bit Gems". It'll explain everything.
I love using a certain ROM emulator site for all my NES/SNES/etc. games. They even have a master pack for each system you can DL and then pick and choose your ROMs from it. Saves time. Again, google it. I can't name/link to it because of forum rules. So I won't. Before I used my PC to emu my games, but the 3DS & DSTwo changed all of that.
And yes, the DSTwo can play all of them. The DSTwo+ can do it better. Especially for the 16-bit games (SNES, TGFX16, GENESIS/MASTER DRIVE). You can even play MAME arcade games like X-Men and Turtles In Time from the arcade and not just the Nintendo ports. As for N64...
...I'm shocked that Superkard didn't focus on the N64 rather than the 3DS. They would have covered a market that nobody else has.
Ahh the N64... the birth of Smash Bros.
How many N64 spaceship controllers have I fixed just so ppl can still play it... (eBay, check it 4 cheap parts)
Hope this helps...