Can't say I've found much use for Dracula aside from figuring out the calculation physics in this game (and for that purpose, it's been INCREDIBLY useful). You'll probably get more of a joyride out of the STK because of the mobility and power, though your ammo costs are also going to be increased by 50%.
You'll have 10 seconds to recover health equivalent to 60% of the damage you can deal out when the Dracula isn't activated. In other words, if you make every single one of your bullets hit with the M-27B1, you're going to recover 24,706 HP. Hmm, not bad o___O Problem is that you'll need to last another 2 minutes before you can do that again...