From reading the boards, I am understanding that a 1.5 LR atty burns hotter than a 2.0. Where does a regular atty rate as far as how hot it burns? Also, in terms of LR or not, are there other differences in the way they perform?
With the 510 model (the 306 also fits the 510 connection) the regular 510 atty meters from 2.1-2.3/2.4 ohms. So anything beneath that is considered 'LR' and they have ohm ratings at 1.5, 1.7, 1.8-1.9 and 2.0. The lower the number the higher the heat, and the higher the heat the more vapor. However, too much heat can destroy some flavors - esp. the lighter ones - fruits/berries and some flavors -
tobacco, coffee are enhanced by more heat. However, I've found that even some of my stronger flavors lose some flavoring at 1.5, whereas they hold up well at 1.7Ω. That doesn't seem like a big difference but when put into the formula for Watts - voltage/ohms x voltage - it can make a big difference. The resultant wattage is what really matters as far as heat and flavor goes - I find that anything above 8.5 Watts will start to show a decrease in flavor although the vapor is great

Also the higher wattage you go - the more chances of burning out atomizers/cartomizers. So there's always that trade off and it's up to you to find your happy medium.
High Voltage
mods 5,6, and above can get high wattage without using LR atomizers and hence can be less stressing on the atomizers however, even though the higher ohm'd attys used in HV
mods may be more stable, since the voltage is also greater - the stress on even high ohm'd attys will be great as well. For me, it's a toss up - and is more dictated to what PV's you have now and how much you want to invest in either HV mods or a few more attys from time to time.