I have a WAS 901 chest rig with the back panel. Best of both worlds that way, you have the smaller, lighter chest rig with the added protection and MOLLE real estate of the back panel. I got mine as a set on ebay for £70ish if I remember correctly. Choose your pouches wisely and you'll be fine. I run two double M4 pouches (I can carry up to 8 mags at a time), a double pistol mag pouch, triple 40mm grenade pouch and a torch/suppressor pouch and there's still space on the front!
If you only use the lower part of the chest rig you can fold the "bib" part down and tuck it away inside.
You could also look at things like the Condor Recon rig which has mag pouches permanently attached which while a little less versatile is certainly cheaper (under £40 from Military 1st).
I guess it's partly down to looks, partly down to practicality. I find a plate carrier is too sweaty to wear all day - a chest rig with just the straps is certainly lighter and airier!