Have to say it depends what you are after.
I had already done my PPL at a rather busy ATC airport, and so really enjoyed doing my Flying Scholarship at Fife, learning on a small strip has its advantages such as precision, but then again Perth has a nice small grass strip too.
With regards to the odd circuit at Fife, I have to agree it is quite different to normal approaches (although it can be more fun) and so maybe learning on a skewif circuit isn't the best option.
As my good friend FJW says I've never been to PIK or Cumbernauld, don't intend to go to Cumbernauld for reasons that aren't important here, but I do intend to go to PIK, I hear it has a lot of benefits and its in a pretty cool place.
One thing I would say about the Tayside set up is (and this may not be true) that ive heard it tends to be a bit of a "sausage machine" for the scholars, and so a lot of instructor time is devoted to them, I gather at PIK you have the instructors time completely to yourself.
What I would say is, decide if you want a small or large airport, a busy of quiet one, one with a grass strip or not, and so forth, get sorted what you want from the place and them cross check it with the excellent comments above, especially FJW's, he's done a lot of flying in all these places.
Enjoy the PPL, I know I'm going back to the land of the scots as soon as I can afford to!
Regards,. .Rusty.