I think you made a good choice to try the Perri's leathers.
1-Beval's Princeton line is not very high quality.
2-You probably won't be oiling your leathers much (if at all--prevent stretching), so I think the slightly darker color will match your oiled newmarket saddle better.
3-I've heard good things about Perri's quality in general. I believe they use domestic leathers and stainless hardware.
4-Like you said, if they don't work out, send 'em back!
Monte - 15 year old Paint/TB
Auric - 13 year old Arab