Some great advice for you to consider but I would be careful in basing any part of your decision on the possibility of a job with an airline. Nothing is guaranteed within aviation. While is it is good to hear that tayside have an agreement in place with Logan air I would not for a second factor that in to the decision making process. NOT FOR A SECOND! Indeed LE recently provided some new FOs to Logan from there instructors.
Both tayside and LE are good providers. The fact that both will most likely use the same examiner for your commercial exams means both will have to train you to a high standard, that much is assured. You will find that people who used to work at tayside now work at LE, and possibly vice versa.
Best of luck.