Olympic might be cheaper, but remember that you would have to travel to/from Thessaloniki for the sim bit, and that's probably going to set you back more than going to either Spain or Britain.
Something that's got to be taken into account as well is the TRTO's reputation where you intend to find work; airline recruiters are usually creatures of habit, therefore they would usually favour an applicant that has been through a TRTO they know. For intance, most FOs with Aer Arann have been type rated either through ATR or through Skyblue; same goes for Air Contractors. Most, if not all, Atlantique crew went through Skyblue. Same goes for Aurigny. Why? Because the airlines were satisfied with the calibre of applicants issued by these TRTOs, and they don't see any reason to change now.
As has been mentioned, Air Wales' demise has created a (temporary) glut of ATR-rated applicants to other ATR operators; though that will subside in due time (some of them have had offers from non-ATR operators), now might not be the best time for the rating, unless you already have some very specific contacts.
Cheers
