Size of generated binaries for OpenSSL 1.0.2d
libeay32.dll x86 in bytes
VC09 1254912
VC11 1252864
VC14 1256448 <- bigger than VC11 by 3584 bytes
libeay32.dll x64 in bytes
VC09 2080256
VC11 1950208
VC14 1947136 <- smaller than VC11 by 3072 bytes
The compiler/linker is about the same as VC11 for speed. As for the binaries, I haven't benchmarked them (and probably won't).
I haven't built Apache yet, have been doing all the dependencies and now it's too hot without A/C to use the desktop. I really need a new laptop cause it's slow with VC9 and would probably be slower than a tortoise with VC11 or 14. It's been on the wish list for some time now but I haven't got the $$$.