I'd personally go after the smaller layout but that's because I find TKL to also be a little on the big side. 660 already has arrow keys, and some navigational keys - other keys that TKL has that 660 doesn't have I really don't use.
Also, I personally would only get a 660c because of nonstandard keycap lengths on the bottom left of the 660m series (so in regard to strictly Cherry MX switches, I would probably go with the 700.)