RAAF used Bostons alongside USAF B-25's in New Guinea to good effect in low level strafing by all accounts. I believe the B-25 was first modified for extra forward firing armament (bombadier replaced) specifically for this combat region, whilst later the A-20G (bombadier replaced by more forward guns) appeared in New Guinea for the same reasons as the primary type alongside 75mm equipped B-25 gunships in the later period (about 1944).
Targets were mostly Japanese merchant shipping, the primary strategic objective of bomber forces based in New Guinea, which I imagine are not heavily equipped with AAA, and rough forward airfields improvised by Japanese Army air forces mostly, which similarly wouldn't have anything like the kind of AAA one might expect in the Reich.
The benefits were obvious for the area, great combat radius, sturdiness and reliability you get with a solid twin-engine aircraft, good weapons loads, you needed these things in the South Pacific where half the time single engine fighters aren't likely to make it 700km or more back to home base if they get any combat damage, whilst the land and sea regions in between aren't exactly very hospitable. Ditching often meant death even if you aced your mission and blew up the enemy.
The Japanese often were forced to improvise light-medium AAA using 25mm naval mountings in triple and double carriages, naturally they weren't always available. Often forward posts relied on things like 20mm anti-tank rifles as improvised AAA and small arms. Other than this they had a 75mm FlaK iirc at major bases. Ammunition was also a serious issue, supply problems of every type at their myriad of field bases dotted all over the Pacific. The American tactic of taking out their merchant shipping and island hopping was just perfect. In the South Pacific airfields frequently ran of out ammunition that was 12.7mm and larger and were forced to scavenge 7.7mm light guns from spotter planes and fit those to their front line fighters. For example the Ki-43 series initially featured 2x 12.7mm guns, but in the South Pacific many had one gun replaced with scavenged 7.7mm guns during 1942 because of ammunition shortages, then later from 1943 they had both guns replaced with 7.7mm to be used as armed reconnaissance models because the only surplus was in lighter calibre ammunition in the field.
In the South Pacific the strafing versions of the B-25 and Boston bombers have an excellent combat record and were a primary offensive type, probably more valued than single engine fighter models. But then in Europe even a Messerschmitt isn't going to be taken down by a .50-cal defensive gun anywhere near as easily as a Japanese fighter. And then is the sheer proliference of the German FlaK corps, where the British had developed radar and centralised command as a basis of home defence, Germany had traditionally relied on FlaK defences and these were highly developed and numerous, continuing their evolution throughout the war. You just can't compare a FlaK-38 with the Polsten, the sheer proliference of SPG FlaK-37 mutes the impact of the Bofors, and that 14.7km lethal altitude of the FlaK-41 plus those super-heavy 10.5 and 12.8cm FlaK used in Reich defence, well they're just terrifying.
