@xarqi- once you take a single sentence out of context or remove all other references- yep- it boils down to that. But the OP's statements were about 5D II / 5D III and in comparison to a 7D. So, until you can get plug in sensors for the Canon DSLR line- yep- one has to assume that a 7D uses a 18mp APS-C sensor and a 5D II/5D III uses a full frame sensor in the 21/22 MP range. And then at that point- yes- you win thru pixel density. The OP's statements about throwing in a TC to make things equal- well- if you could stick a TC on a 5DII with a certain lens and use it- you can certainly do the same with a 7D, for example, and end up with more usable pixels. I know, everyone talks about the clarity of a full frame pixel - but it's still just that- a pixel.. Granted that what he says may make sense if you can fully frame the full frame using a TC- with what the desired outcome is- then what he says may make sense. If you are still short or focal length limited- then my point is why would you not leverage a modern crop sensor's advantages of higher pixel density- and get more pixels on target ? Because larger dots from full frame are better ? It's a pixel. Basically- a dot. Ridiculous to believe a dot or single from a full frame camera is better than a dot or single pixel from a crop camera. But if you are into just arguing semantics- well, I probably have better places to waste my time.
@sambarino. Will all DSLR's be FF ?
Lose the APS-C format cameras- and there goes all the sales of EF-S lenses. The alternatives- third party glass and EF glass- most of which is L. Pricey alternative. OK, some will bite the bullet and buy into EF glass- but many more will walk away. Good for Canon's pocket book ? Nope.
Entry level kits- like the T3, T3i, T4i, etc. This is where most entry level DSLR users are buying into. Without cheaper entry level cameras- most would be relegated to buying either used or none. A lot that fall into this category don't ever buy another lens- or if they do- they buy one- like a 55-250. Most consider flash- to be onboard flash. One or two kit lenses and perhaps a flash- for most- but not much beyond that usually. As far as buying used, the last time I checked- Canon does not make money off from Sam selling Pete a used camera. OK, sometimes sales of a used camera does make it into Canon- indirectly - because someone is upgrading. How about those that aren't ? Or those that are switching flavors ? Nope, it makes Canon no money in those cases either. What would a FF entry level kit look like ? 18MP full frame, with a 24-105 lens on it. A t3i kit- with a 18-55mm ef-s lens- is currently around $750. A lot of people scrounge up to be able to buy something like that. The 24-105- new- goes for about $1050 today. So, Canon would have to sell a body and lens for less than it sells the lens today??? Or develop a cheaper EF lens to put in kits..
EF glass. Perhaps you believe that EF glass is going to get cheaper. From what I've seen lately- it's not really the case. Have you looked at the new price on a 24-70 that you can purchase and get shipped now- and the newer version that is being delayed ? Good news is that older EF glass will be worth more- bad news- Canon does not make money off from used lens sales either.
Development: If full frame only was planned for the near future- why would Canon be developing EF-S glass still ( like the EF-S 18-135 STM's ) This in itself tells me that Canon is planning on keeping EF-S around for a while. Otherwise, you'd be seeing a 24-105 IS L STM (mark II ) lens instead.
EOS 5D III, EOS 7D,EOS Rebel T4i, Canon 70-200 f/2.8 IS II, Canon 24-105L, Canon 18-135 IS STM, 1.4x TC III, 2.0x TC III, Σ 50mm f/1.4, Σ 17-50 OS, Σ 70-200 OS, Σ 50-500 OS, Σ 1.4x TC, Σ 2.0x TC, 580EXII(3), Canon SX-40, Canon S100
Fond memories: Rebel T1i, Canon 18-55 IS, Canon 55-250 IS, 18-135 IS (Given to a good home)...