Having graduated from GLMA a few years ago, sailing on my license on the lakes and deep sea, deep sea is much better. Schedule on the lakes sucks, 60 on 30 off (if your lucky). The people are MUCH more miserable in general. Obviously you find grumpy people deep sea but more so on the lakes. The job itself on the lakes I loved, piloting down the rivers and in port every other day or so. Although the most of the ports are nothing to write home about. The seasonal thing a is actually not what someone else wrote, the lakes only close from January 15- March 15. Very rare do those dates change, this year being one of the rarities. Deep sea you make more money, obviously depends on the company, but on average, more money deep sea. The place you go are endless and usually are awesome.
Anyway, your decision where you want to work shouldn’t affect what school you choose. I’ve never been to any other school, but GLMA is amazing. Small, which is nice considering everyone knows everyone by name. Plus traverse city is awesome. It is a huge bonus to go there and graduate with first class pilot on your license even if you never touch the lakes, it looks good for interviews and possibly opens more doors.