I just got one of each, and the VEPR is nicer out of the box for me. The SLR is super nice still.
The only con with the VEPR is its heavy. The SLR is the lightest AK Ive ever had, noticeably lighter than my "was" lightest WASR-2 with light plastic furniture.
The VEPR was perfect out of the box. The SLR has two little annoyances but otherwise works great out of the box.
1. The spring loaded pin holding the barrel nut on won't go all the way down so I cant get the nut off. Maybe Im doing something wrong.
2. One of the magazine guide rails sticks out too far and you have to push sideways on mags to insert them. It was easily fixed by dremeling a hairs width off of it, but still annoying. Two others have reported the same thing on AKFiles. I cant get too irritated about it, I had a Saiga 762x39 with the exact same issue over ten years ago and I consider Saigas top quality.
If the VEPR was lighter I would say the VEPR is a more desirable gun, at least to me...but the lightness of the SLR is a fantastic. It reminds me of a Colt 6720 as far as that goes.
Edit: The other thing with the VEPR...mags insert easier than any AK Ive used, and they are tighter/have the least wobble Ive seen. You'd think those two things could not exist together, I don't know how Molot does it.