I love Hyatt Harborside, and rarely stay elsewhere. (so I am not qualifed to evaluate it against your other choices!)

Based on your list of importance:
1) if you mean a nice lounge where one pays for food and drinks, the lounge in this hotel has a spectacular view of the city with excellent food and beverages. if you mean a Club lounge, where food and drinks are free, this hotel doesn't have one. (Lounge access is important to me too, but I am more than willing to trade it off for other amenities this hotel offers.) You will get full breakfast in the restaurant.

2) indoor pool, usable during your visit

3) I always book the cheapest room, and am always upgraded to a room with a great view of the city.

4) it is AT the airport, super convenient. If you want to go into the city, you can take a cab or (better yet) the water taxi.

5) I generally get excellent rates here. Continue to check, as there are often last minute deductions.

hope this helps - enjoy BOS....and Aruba - you will love that Hyatt, too!