Which one of the following DSLRs should I go for and why? (Price doesn't matter)?

1) Nikon D3200
2) Nikon D3300
3) Nikon D5200
4) Nikon D5300
5) Canon EOS 1200D
6) Canon EOS 1300D
7) Canon EOS 700D

Whatever you choose - choose Nikon.

If price didn't matter, I'd go for a medium format dSLR first and if that was too much, I'd settle for a full-frame one instead.

Those you listed are all bottom-of-the-barrel models. If this is your first dSLR, avoid all of them. Entry-level refers to budget not skill. Go for a mid-level model instead like the Canon 80D, Nikon D7200 or the Pentax K-S2 for more satisfaction.