I know, asking for opinions is different from asking for facts, but I've enjoyed the knowledge and perspectives shared on this board, so I'm hoping a few folks will pitch in with opinions. Well, other than, "Gee, that's not even a very smart question."
Background: I currently possess 2 crop sensor cameras:
Panasonic Lumix DMC-GX85 with 3 lenses:
Lumix G X VARIO 1:2.8/35-100 POWER O.I.S.,
LUMIX G VARIO 1:4.0-5.6/100-300, and
kit G VARIO 1:3.5-5.6/ ASPH. MEGA O.I.S.12-32mm (.02m/0.66ft-infinity)
(all purchased new a few years ago from Mikes Camera in Boulder, CO).
Canon EOS 60D with 2 lenses:
Tamron SP AF ASPHERICAL XR Di LD (IF) 28-75mm 1:2.8 MACRO (camera and lens bought inexpensively used in separate transactions locally) and
(freshly received from KEH) a nice used Canon 55-250mm F/4-5.6 IS II.
Camera inspected, cleaned, & adjusted by Key Camera in Longmont, CO - rated "nice".
Interestingly, I've learned that the crop factor on the Canon appears to be an industry-odd 1.6, most other brands being 1.5, but the Lumix (like Olympus) is even more extreme at 2.0. I think I'd like one of my two cameras - not really being able to make a case to own three - to be a full-frame camera. While I have well over $2k invested in the Lumix kit, I have only a few hundred in my old Canon stuff, so my obvious choice for replacement is the 60D.
Here's the question: IS THIS A GOOD MOVE? I have a chance to buy a professional's back-up Canon 5D Mark II with low shutter count for $600, and I would try to sell my 60D.
I'm enjoying the 60D. Purchased a manual for it. The 2 lenses are fine for this learning stage, though I'd need to add a nice wide prime before long, I think. But the flexibility of a full-frame, some greater potential in image quality and in landscape scope ...these things tease me toward trying the 5D, even if it is an out-dated one (though hardly more so than a 60D, I guess).
If I'm going to make the move, maybe now is the time before I invest in more EF-S lenses. What I have, I imagine I can sell. The Tamron, I think, should work on the 5D. He has a 24-70mm f2.8 L USM available too, but I don't think I can afford the price of both camera and lens at once. (Is $650 good for a properly used specimen? It's much bigger and heavier than the Tamron. And it didn't totally kill the Tamron in a head-to-head by Bryan Carnathan
https://www.the-digital-picture.com/Reviews/Tamron-28-75mm-f-2.8-XR-Di-Lens-Review.aspx)
Sorry. Looong question.
Any kindly opinion is welcome. A silent chuckle is OK too.