+7 dex mod? Are you using one of those REALLY light armors (haramaki, padded, quilted, etc.)? Then currently, it heavy armor would give you more general AC.
The general armors that I know of with 7+ max dex all have +1 AC. You might be able to mithral or something with a few, but generally, it will just go to +2, so little difference. So looking at the armor and dex, it would be 7+1=8.
Full plate is 9+1= 10. So it is slightly better- that is just how light armor usually works- very stat dependant, and most of it still doesn't match up to the acceptable stats versus actually good heavy armor (especially if you use core, and non of the eastern stuff).
This all changes depending on what you have access too, of course. Celestial plate, as a particular magical item, has both decent AC and max dex. And there are likely various tricks for getting something more competitive.
This isn't to say that you should go with heavy armor- you might just not have the proficiency, and you might prefer having good touch AC over good flat footed (you might still have uncanny dodge, which makes that comparison better).
Honestly though- maybe they should have given you a mithral breastplate or something. Practically everyone that isn't a wizard or monk can make use of a nice mithral breastplate. -1 isn't that bad, and could be covered by anything that decreases ACP (such as the armor expert trait).
Just read somemore: Wait, this is Half Plate?
Yeah. No. Don't.
That is 8+0=8. The exact same as the most barebones light armor, with none of the touch AC benefits. There is a reason why full plate is that standard for heavy armor.
(resulting in the loss of a paladins power because he broke the law, but what you going to do)
Your DM does realise paladins don't lose their powers for breaking the law, right?
"A paladin must be of lawful good alignment and loses all class features except proficiencies if she ever willingly commits an evil act."
I, personally, would be very upset at this, but each to their own.
*edit*
don't forget that heavy armour will cost you in terms of armour check penalty quite severely. IF you are using any DEX skills like acrobatics, stealth etc, the full-plate is going to hurt you quite a bit. Mithral breastplate would be a lot nicer honestly.
Wait, it's half-plate. What a complete waste. Don't bother.
If your path is either champion or guardian you can pick up the path ability armor master, but it will require multiple choices to use heavy armor. You could get mithral plate and only need to choose armor master twice to get your full DEX. You could also pick up the mythic feat dual path to get access to armor master.
Just a note... you cannot use Acrobatics in any armor that reduces your speed...
Yeah, mithral breastplate is a fantastic stepping stone prior to celestial. It is 6+3+2=11. It is pretty much the best for a dex build until you get to +11 dex mod (which means you would need 8 more dex- that takes time, maybe enough that you are eyeing celestial instead of padded).
It is big enough that it comes off as proper armor, expensive enough to be on a noble's budget, and light enough that anyone could enjoy it. It works well as a 'badge of office' when it comes to combat uniform.
Just a note... you cannot use Acrobatics in any armor that reduces your speed...
you just cant use it to avoid attacks of opportunity. other than that all uses of acrobatics are still valid in medium/heavy armour.
agile breastplate is nice if youre going midling.
hellknight plate if you can swing it for your GM (it's fullplate but with better ACP)
mithral/celestial/etc is great with good dex.