I was in your exact shoes 2 years ago: I sold my 2120 and was looking to go up in size. I lamented back and forth between the 2520 and the 2820. I decided to go with the 28 pilot house and started looking. I found a steal on a 2830 ( extended pilot house 28') and bought her.
She was TOO much boat : she handled effortlessly w/ twin 225's. She was fast, nimble, but THIRSTY! She would get 1.4 -1.5mpg (which was fine when I had a 3 or 4 man crew).
But, for just cruising the river with my son, she was too expensive to operate. A simple inlet run cost me $140 in fuel. My son and I like to run the river to the inlet ( 29 miles one way). So, it made those exertions expensive.
I sold that 2830 and bought a 26' center console: not a Parker but rather a Jones Brothers Marine with twin four stroke 150's. Love this boat, but I miss my pilot houses. I will be selling this jones brothers soon. I will be getting back into a Parker pilot house. Now, I'm just tossed up between the 2320 ( so easily towable for s. florida runs) vs. the 2520 which would give me lots more room and one extra angler. I think I am going to go w/ the 2520 DV next w/ a single 300 and a 9.9 kicker on the bracket.
Just my insight who's been in your same "predicament".
Best wishes on your choice. The 2820 just cost too much money to operate on a casual basis. 2520 seems an excellent compromise. Parker/ Yamaha claim 2.1 mpg at 34mph cruise in the 2520 w/ single 300. Sounds good to me!