B-17 is my least favorite bomber - heavy, slow, trading bomb-load for defense armament. Its has only two strong sides: firm airframe and good defense armament. Its huge range is irrelevant for AH as there are no real strategic campaigns (beside SEA) and bomber use is purely tactical.
I like flying bombers - but when I fly bomber my mission is to destroy/damage a target and almost never want/try to get kills. I consider my mission as most successful when I don't even met a fighter in a way it can endanger me.
If you consider your job making efficient and effective damage to enemy targets than B-17 is least suitable bomber for the role as per player. It has huge turn around time due to slow climb/speed vs its payload.
My favorite bombers to get the job done are: Ki-67, Boston III, Tu-2S and of course Mosquito XVI and Ar-234.
How are they different - it isn't about defensive armament - the guns are your least level defense, if a fighter got into shooting range and he is skilled enough - your chances are slim unless you super sniper (and most aren't)
Their defense is planning and speed: approach the target, get in, destroy the targets, get out and land. Shooting fighters at air-to-air shooting range IMHO is last resort.
Additionally being fast they allow much higher bomb delivery with survival generation rate per-player hour in comparison to B-17. As I can do several sorties in Tu-2, Boston or Ki-67 from much closer fields so I can bomb at relatively safe altitude with high survival chances in comparison to B-17 that have long climb to do.
My $0.02