I perfer LP tanks. Less expensive, easier to get a good fill, and often easy to get a real good fill! ALso known as a cave or wreck fill.
But the first thing you need to do from the sounds of it to get better air consumption is to RELAX on your descents, and do a proper weight check! It sounds like you may be struggling to get down and get comfortable. That is often a training issue for new divers who have not been taught proper weighting, rushed through training, have not had enough instruction in proper buoyancy and trim, and are put in open water too soon.
A different tank is not going to help in those areas. It's a gear band aid to a skills problem and doesn't really address the issue.
As far as tanks do go though if you really do think you need more air you need to figure out how much more and go from there. Pressure is not as important as size. You need to figure out your SAC rate. Resting, working, and average them. Decide if you want aluminum or steel and then find out what kind of fills you can get. As Steve noted not all shops can or will fill a HP tank to it's rated pressure.
LP's you don't have that issue. Most everyone can fill to 3000 PSI and will do so. I like LP 85's, LP 72's, and LP 95's. I have all of them, and just picked up a pair of lp 75.5's for my sidemount rig. These are all rated a 2400 psi with a plus rating of 2640.
Taking the LP 85's if I get them filled to the normal fill of 2800 that can get easily here they are now 90 cu ft tanks. If I fill them myself to 3200 for a wreck dive in the Great Lakes I now have 103's.
Something like a HP 100 is only that if I get a 3442 fill. At 3000 it is only 87 cu ft. And it was more expensive. If the shop gave it a hot fill and it cools on the way to the dive down to 2800 or so it's now only 81 cu ft. Whereas if a hot fill of 3000 in the LP 85 cools to 2800 I still have a 90 cu ft tank.
I suggest reading this article before you buy tanks -
NWGratefulDiver.com
It's by SB member NW Gratefuldiver and is one of the best articles I have read on the subject. I use it in teaching my OW classes.