If you are happy with your BCD, find another shop. This one is obviously more interested in selling you new equipment than meeting your needs. Also there's nothing wrong with a weight belt.
That said, if you want to switch, I'm one of those who will advocate for a backplate plus wing (BP/W) and harness. The following video is a pretty balanced comparison. Make sure you read the comments to get the full picture.
It's worth noting that since you are in cold water, a stainless steel backplate will let you get rid of 6-8 pounds of lead. This is probably the best deal on a complete BP/W setup ($424 with a stainless plate).
DGX Custom - DGX Gears Singles Harness / Backplate / Wing Package