I voted for the 5" Classic for range use because it has less muzzle blast to shooters on either side of you.
With the V-comp, wouldn't the 4" barrel with the comp attached be about the same length as a classic 629 with the 5" barrel? It seems like the difference would be that with the comp it would be louder and might have a little less velocity. And with the 4" barrel, you would have a 1" shorter sight radius. So it would seem that unless you are occasionally going to enjoy the convenience of the 4" barrel without the comp attached, there would be little advantage to getting the V-comp (unless you just like the looks, of course.)
Either barrel porting or a compensator attached at the muzzle can reduce muzzle rise during recoil and both make the muzzle blast sound louder to another shooter standing next to you on the firing line. It can seem pretty obnoxious or downright painful to the guy standing next to you. However, I have been on the firing line with a shooter on my left firing a ported 629 (4" barrel) while a shooter on my right was firing a 629 with a 2.5 inch barrel. Both were using magnum ammo. I didn't have a decibel meter, but the the snub sounded as loud or louder to me than the ported barrel. Strangely, people only complained about the noise of the ported barrel but not about the equal or perhaps greater blast emanating from the snub. I left the line after hearing two shots from each revolver.
It's been several years since I have fired a 629 with magna- ports or with a S&W style comp. But IIRC, the comp was a little more effective than the magna-porting (which had 4 trapezoidal ports, two on each side of the barrel) but it didn't direct as much of the sound to the side to blast the adjacent shooter as badly. When I fired a magna-ported 629 with 6" barrel with only one trapezoidal port on either side, I didn't think the porting reduced the muzzle jump or rearward thrust of the recoil to a significant degree. However, with only two ports total, the ported barrel didn't sound much louder either. On the 629 with 4" barrel and 4 ports, the blast seemed much louder, but the reduction in muzzle jump seemed much greater as well.
Whatever you choose, always wear earplugs plus earmuffs when shooting a magnum revolver, with or without ports.
