Tiffie is more or less equal to Dora around 10k, alot better bellow 5k.
Tiffie Turns even slightly better then the 190 A5 in sustained turns, it accelerates far better.
You claim that the combat time of it is very limited, take off with 100% fuel and 2xDT's and you'll have more then enough when you reach your target, even if you climb away and get 20k alt before you reach the target you will have more then enough. Specially at those ranges the fights are in the MA.
When it comes to guns, you say it's got 140 rpg, well, true BUT it's got 4 guns, it's got 4x140 and it's got better guns wich are both easier to hit with and cause more dammage then the guns in the 190.
If you wanna test ammo duration, you only fire 2 guns at the time since that is the number of 20mm the Dora has. Belive me, the Tiffie ammo will last longer.
4x140 = 560 rounds total, fire these 2 guns at a time (wich will give a better result then in the Dora) and you're ammo will last longer.
Allso, the 13mm in the 190 adds up to the weight, although they can cause pretty good dammage on straight flying planes where you can get a nice close hit square they or often useless in B&Z where the enemy sees you and turns away, what matters there are either cannons (wich the tiffie is superior in, no matter using 2 or 4 at the same time) or alot of 50 cal guns such as the US planes.
If you get rid of teh 13mm in the Dora, it gets better performance, but who wanna waste 950 rounds out in the thin air every flight?