Been to both. Fenway is better, but I enjoyed the area around Wrigley more.
This for me.
Have been to Wrigley 2x... once in the bleachers, and once in
pretty much the best seats in the house (dugout box, aisle seat across from owners seats, up against the brick next to Cubs on deck circle).
Have been to Fenway countless times having sat in bleachers, RF Grandstands, 20ish rows behind home, Bud Roof Deck, etc.
Have been on the field at Fenway during BP.
SEAT COMFORT: Wrigley
PARK ATMOSPHERE: Fenway (Visually more interesting park, more amenities, etc)
SEAT VIEWS (overall): Fenway*
PARK AMENITIES: Fenway (Rehab did wonders for the stadium without killing historical vibe)
SURROUNDING AREA: Wrigley (LOVE Yawkey but Wrigleyville has edge overall).
FAN BASE / CROWD VIBE: Fenway (Bleachers are FUN, but most cubs fans don't care too much about the game)
OVERALL PREFERENCE: Fenway
I'm obviously biased... but I genuinely prefer Fenway, teams aside. It's just a more interesting park with a much better gameday vibe if you're there for the game. If you're just looking for somewhere to get white-girl wasted on overpriced beers, bleachers at wrigley are the spot.
*Disclaimer: You have to dodge certain seats at Fenway (RF GS 3 thru 7 for example) and obscured seats (duh)... at fenway.