It depends on the type of diving I'm doing.
HP100 is probably the best all-around tank. Double them up and you're good for every kind of diving except extreme tech and serious cave/wreck penetration. But they won't give you the kind of long term back problems that double hp130s will (or double lp108s)
That said, I prefer my HP130s for recreational boat dives where the extra weight is irrelevant and the extra BT is well worth it. The HP100 is a great tank for shore dives, though, they're nice and light.. very handy for long schleps from the car to the water's edge.
The LP vs. HP debate is silly, because the answer is obvious: Buy the tank that holds the amount of gas you NEED, taking into consideration local availability of overfills/"cave fills". Locally (Los Angeles), cave fills are very hard to come by. So it's silly not to buy HP tanks. That said, you still need to look at the actual fills... are they truly HP fills? Or, more importantly, will your HP tank give you enough gas to do the dive you want if you get a short fill, say, to 3200-3300 psi?
If not, then you need a bigger tank. If you NEED 108 cf of gas for the dive you want to do, then get an lp108 and be done with it... OR get an HP130 and be done with it (once you realize the HP130 will give you the 108cf you need as long as you can manage a 2800psi fill). And hey, if your local shops won't overfill LP tanks, you'll always get more gas with the bigger HP tank, because they won't refuse to fill it.
HP100 is a great tank... even at 3300 psi (pretty easy to get), you end up with 96 cf of gas, which is a lot more than you'd have in your perfectly-filled Al.80 (77.4cf), and with a lot less weight on your back than with an lp95 that's been filled to rated limits only.
