Re: TX22 vs TK15 S2
As you say the head of the TK22 is indeed larger than the TK15. Whether this is an issue it will depend how you intend to carry the light.
If you want to carry in your pants' pocket, then the TK15 will be a better option.
Build quality goes: both lights are on par - same Fenix TK series.
UI: is identical as far as I understood. The TK15 has a stepdown after 30 minutes the TK22 after 22.
Runtime: the TK15 will have 20 or so minutes longer runtime - if that's important for you, take into consideration.
Brightness: the TK22 will be brighter though visibly less than the lumen difference on paper might lead you to think.
Throw: the TK15 will throw a bit further but not by much.
Beam: I think the main difference lies here: if you prefer a throwy kind of beam while the TK22 will be floodier.
Overall there is no better between the two lights, I would just choose the one that fits your needs better based on beam and form factor.
Subwoofer did excellent reviews for both lights so you can easily compare datas - it doesn't get better than this when choosing a flashlight!
http://www.candlepowerforums.com/vb...1-Fenix-TK15-S2-Review-(1x-18650-or-2x-CR123)
http://www.candlepowerforums.com/vb/showthread.php?352542-Fenix-TK22-Review-(1x-18650-or-2x-CR123)
Hope it helps!