I think its really a matter of opinion.
We frequent BLT and always do a lake view on the marina side. We refuse to spend the points on theme park views when there are a million places to watch the fireworks from - Roof of BLT, the walkway, the CR balcony at the walkway, any window from the north tower hallways..... you get the picture.
We do like the marina side because many times we just like to lounge on our balcony and....... wait for it...... view the fireworks! Its relaxing to just have some coffee or an adult beverage and be able to chill out in your pjs right on your own balcony to view them.
Also, on the marina side you can see the Epcot fireworks, and the Electrical lake show goes right by, which is kind of nice.
Get the right room and you'll be able to watch the weekly movie on the green from your balcony as well.
On the other hand, if you don't want to spend the points, then Id say stick with your standard view. You could always request a room over the pool, which would be much nicer than the parking lot in my opinion.
Before becoming
DVC members, we always said "we don't go to Disney for the hotels"
NOw that we are in BLT regularly, we don't ever want any less than a Marina Side Lake View.