looking at the questions you're asking, i think it's best if you went down to a dive shop with both types of BCs, and various models for both types. this way, you can see for yourself and (hopefully) the staff will be able to advise you on the pros and cons of the different models.
my jacket BC is heavier than my backplate BC, but i prefer the jacket because it gives me more lift (bigger bladder), and has pockets to stash my stuff.
also for newer divers, they are easier to put on due to the adjustable harness straps (OK, i know halcyon has that funky strap system now, but as a guide - not available for the other BPs), provide more stability on the surface, and generally easier to manage the air in the bladder.
*this is from my personal observations after diving with many divers of different abilities. i'm sure your own experiences would be different.
99% of my friends use a backplate system, and they have to either DIY or spend lots of money to buy halcyon pouches so they can bring their slate, SMB+reel, pocket mask, lure, and all sorts of bits and ends. either that or they look like christmas trees. some need to use the crotch strap, and some don't. the travel series ones with 24lbs lift or less are a little too small for anyone over 80kg with a DSLR rig. fully inflated, my pioneer 27lb wing only lifts me to about chin level out of the water. definitely not for rough waters with my camera stuff.
go have a look, try them out at the pool before you make a decision. and BP systems are essentially the same regardless of brand, so just see how rich you are?