I'm in a quite similar situation. Budget 3000$. Looking for an upgrade to FF, options are: 6D + some glass or 5Dmk3 body only.
I have at the moment 7D, 24-105 F4.0L, 50 F1.4, 28 F1.8, 100 F2.8 macro and Tami 70-200 F2.8 plus APS-C stuff like Sigma 8-16 F4.5-5.6, Tokina 12-24 F4, Samyang fish 8 F3.5. Flash 430EX II plus some studio toys.
I've been shooting mostly for myself but now I'm trying to get some jobs around and it looks there is more coming on the horizon. At the moment I do weddings, events, promo, indoor and outdoor portraits some landscape for prints. While I would be quite happy with 6D for landscape, portrait and promo products shoots then anything else I do is screaming for 5Dmk3
Guys give me please a wise advice as after a weeks of reading opinions about 6D and 5Dmk3 still can't make a decision.