Sony has shown what is possible with new sensor technology whilst Canon hasn't updated theirs in many years and so on. That then leads to people defending Canon doing little or nothing in various areas whilst it leaves others exasperated.
Canon as shown what is possible with lens and optical technology, while Sony has done little or nothing in that area. Some people seem to think bare silicon sensors take pictures…
With the metabones adapters, I can put almost any lens on the Sony A7 series. Why should I limit myself to Sony's lenses?
But... but... but... system! system! system!
Yup, by going down the Sony mirrorless path the options for what a working "system" can be are much larger than with Canon.
If by "working system" you mean massively compromised with severe loss of functionality then yes, you might have a point.
Which pieces of functionality will be compromised?
You obviously haven't practiced what you preach, go use a Sony with a Metabones and try out the AF.
Is there any other loss in functionality aside from AF?
Read tcmatthews reply above. You really do have an incredible habit of talking from a position of no experience of the suggestions you make.
I'm not having a conversation with tcmatthews, I'm having a conversation with you.
I want you to tell me if there is any other loss in functionality aside from AF.
Dude, I tried the metabones + a7 combo and it suxs. Heck the a7 AF suxs period compared to a measly old 5Dc's center AF point. :/ MILC hasn't convinced me of its AF yet and the only hope I've seen is DPAF. (Not terribly quick either.)
You can eat the whole cake with canon or you can eat a little of the cake and have some pie with a sony. Some people just don't like pie in their cake or cake in their pie.