so there is the mini, the 3 and the 3.5. I know the 3 & 3.5 have dual coils and operate at different ohms. Does this make the vapor delivery better? They are all priced the same and I am trying to understand the benefits and drawbacks to each protank. Thanks! Oh yeah- its my birthday!

Thanks ECF!
Lower resistances can provide a warmer, and often more flavorful vape, as well as a larger level of vapor.
Kanger makes coil heads with resistances as low as 0.8Ω, that fit many of their current tanks, but... what's more relevant are the output capabilities of your PV.
At it's base value, a tank is just a holder for the coil/head assembly. If that tank has a good ACF design that delivers enough air for both the heat being generated, and your subjective needs...
and suits your aesthetic and dimensional needs as well, then you have a winner.
I don't use them... but as Kanger is your point of reference, a general consensus is that the Kanger Aerotanks - both Mega and Mini, are excellent in meeting the above requirements, for a broad spectrum of users.
All APVs have limitations in amperage/wattage/voltage/short circuit protection... and all have a lower resistance (ohms - Ω) limit as well.
Lower resistances - and the heating potential for the greater coil surface area accorded those lower resistances - draw more current. In other words, if your APV can't supply the "power", then the coil(s) won't get hot enough to vaporize juice... or the APV will sense a resistance that is below it's capabilities, and not work at all.
Knowing the specifications of your APV (at present) will tell you how low you can go with resistance and still provide adequate current for that resistance. If you have a APV with the DNA30 chipset for example... then you have more than adequate performance to support 0.8Ω resistance, and lower.
If, on the other hand, you have an Innokin MVP2 (or similar performance profile device)... then you have only enough current output available to support resistances down to 1.2Ω.