Here is my 2 cents for what it is worth:
While the tower booms seem like a good idea, it appears to put a great deal of stress on the tower itself and side torque on the boat (with the main attachment point to the boat being further out as opposed to the center/rear pylon). Obviously they have tested these things so they know they are fine but the set-up and removal of a tower boom while on the water is going to be more difficult than the one which simply attaches to your pylon. Also, consider re-sale value, if ever you were to no longer need/want it. A boom which attaches to your pylon is likely going to work on several boat models, I am not sure the same can be said for those which attach to towers as there are so many different tower configurations out there.
One upside to the tower boom is that it is completely outside of your boat.
Again, this is just my observation and others may have different opinions/arguments. Good luck, either way going with a BFI product and the customer service of Seipel and Bowers is good.