the XL is marginally better than the regular 3DS, I can attest to this.
Whether it's a good buy depends on your taste in games. There's a lot of good RPG's, Puzzlers and Fighters currently, with more coming out.
The 3DS library is mostly casual, and may lack whatever type of game you like to play, so check out the library.
In my opinion, yes the 3DS XL is a good buy.