All I can tell you is I installed three D31M blue top marine Optima's in my TR21 about 6 months ago.  I spend long hours using a three way rig that requires a lot of trolling mtr use. At the end of the day the power settings feel the same as when I started. They recharge much faster, are lighter and smaller. 
If you are going to keep the batteries a long time (in that boat or move them to a new boat) they are worth the extra money. I have a red top in my Jeep that is 8 years old and still going strong.
I was really tired of the hassle of topping off the battery water every month.  A TR21 with four batteries leaves very little room for access.
That's my 2 cents.

Trogan,Trogan
RB