I haven't tried Scuba Pro, but I have a 3mm Pinnacle Merino, Seal. The Pinnacles suits are well made, and I believe the Merino lining keeps your warmer. The seams are glued and double blind stitched, which allows less water to flow in and out, supposedly keeping you warmer. I have dived over 100 dives with my Pinnacle and would buy another one. My only complaint is that the stitching started to unravel after one dive trip. My local dive shop sent it off to the manufacturer and they reinforced the seams which have held up.
As for the Merino Elastiprene, I tried the 3mm on at the LDS and it didn't fit me like my Seal. Oddly, the Elastiprene was uncomfortable and fit terrible. Even though the manufacture might have a well made suit, the fit is the 1st part of the battle for me. If the Elastiprene fits you well, you should be happy with the suit.