I would think either are fine - it really comes down to the interface you want. The TK15 has slightly higher max output, but that could just because it is a newer sample (i.e. there may have been some circuit tweaks from the original version TK12).
Thanks for your input and especially the thorough review of the TK15. I did purchase the TK15 and I think I will be happy with the light for its purposes. The only design weakness I have discovered even worthy of mention is the front switch. It is indeed difficult to locate, easy to use but yet difficult to locate. I think my next pocket light will be the PD30, as the quality of the TK15 has given me confidence in the Fenix brand. Thanks again for your input.