Photography is a hobby for me to ENJOY. So I weigh my purchases with this question in mind: Will this piece of gear enhance my pleasure from my hobby?6D hardly a 'heavier' camera plus the 100L looks beautiful on a 6D : }
For for example, when I asked myself if I should upgrade from the 550d to the 6d - the answer was NO. For what I do - having a FF heavier camera will not make any substantial contribution to my hobby.
On the other hand I purchased a 100L - and enjoy it immensely.
I know don't think I'm immune to GAS (Gear Acquisition Syndrome) - But I'm on a budget and need to spend carefully.
It's good to be careful, because once you take the full-frame 'leap', all hope for control of GAS is lost.
5D3, 5D2, Sony α6000, G16 | SY14 f/2.8, Ʃ20 f/1.8, 24 f/2.8, 35 f/2, Ʃ35 f/1.4A, 50 f/1.8 I, Ʃ50 f/1.4 EX, 100L Macro, 17-40L, 24-105L, 70-200 f/2.8L IS II, 1.4x II, 70-300L, 100-400L | E-mount: SY12 f/2, Ʃ19 & 30 f/2.8 EX DN, 16-70 ZA OSS, 55-210 OSS, Metabones SB | FT-QL, AE-1P | FD(n) & FL lenses