For me :
SE100 is fun and makes decent money
XFL-1 is Very fun and makes decent money. Love the 37 mil
A6M3 - Most fun at T5, awesome guns coupled with awesome manuevrabulity= profit and makes me overlook the bad handling at higher altitude (sometime necessary on some maps with lots of heavies and bombers).
Blenheim bomber - is fun for seal clubbing at lower tiers altho' it doesn't make that much money
AR197 - is fun for T4, good alround multirole. Feel a bit guilty because it's also ood at seal clubbing
A26B - Very good credit earner and fun to play. Many times I go hunting other bombers and the defense is really good at same tier ( T7 heavies will still shred you in no time)
VB10 - Has very good firepower and great high alt climb and speed. It's fun to play. Decent credit earner
J4M - It's kinda meh so I can't usually get good games in it which means lowish income. Maybe it's just me.
I207/4 - Is insanely good at T4 but easily counterd by T5.
BF110 C-6 - Nice for long range sniping and T4 bulying but easily outclassed by T5's.
M8A1 - Fast and somewhat maneuvrable but very very weak guns.
Do17 Kauz - Fun heavy, ofc it does not make good money (it's T3 afterall)
XF4U1 - Weak guns, sluggish I don't like it at all = bad at making money even if it's T5.
AD10C - It's very maneuvrable and funny looking. But it's sloooow. The rear gunner does not get much use since it has weak guns and the plane is anyway better at doing dog fights which means the rear gunner cannot bring guns to bear on enemies except occasional snapshots. But it's still fun to play overall even if not a good credit earner.
Ki-43 chinese - It's a Japanese Ki with weaker guns. Not recommended.
Venom - Insanely good at dogfightig although it must get very close to the targets (400m) and may die in the approach if heavies or spitfires get a good pass at you. But overall is fun.
Spitfire Ia - kinda like the Venom but it seems with less agility.
Other lower tier premiums are not worth mentioning because.