Renovation - Spray foam or Batt Insulation! Advice please!

It can be a complicated question, but my short answer is that it's not worth the money if you're not doing the whole house. The benefit is that it seals the house from air infiltration. If you're not going to seal the whole thing you're paying too much for the R Value than necessary.

If you have areas where you can't get good batt or blown coverage then it can be worth it to do parts - knee walls and restricted spaces.

The only place I've used it on my own house rennovation is on the man-cave / wine cellar which is on the lower floor of an elevated house, but that's simply because I get it cheap and I am going to be conditioning that space to below 60 degrees using a completely isolated unit.