One of the features of the XL and vmod2.0 is that you can use just about any 510 atty. 306's work quite well also.
I like the pro-spec Vapage AMG Hybrid
BF on my Vmod(s) and have found it to be a consistently long life atty (several weeks) with a nice flavorful full vape, so well worth it (especially with the occasional sale). I also use the Hybrid Universal on other mods, even though it hasn't been upgraded to the pro-spec (shi-fu) yet.

If you haven't tried this pro-spec atty -- do so, when they are back in stock for a nice treat.
The Hybrid has been greatly improved, as attested by many on this thread.
The other atty's most often raved about are the aero and the hh357----both premium attys.