A bit of an old thread, but I now own both and can give a side by side comparison.
Overall, I'd say the Gen4 is the better gun. It's more realistic, more efficient, easier to load and has a far better trigger. The Gen4 functions very much like an actual Glock. You insert the magazine, rack the slide and once the magazine is empty the slide stays open until you release it. It's a little lighter than the real thing and the weight is more centered around the magazine rather than the slide, but it's quite close. The slide racks more easily than on an actual Glock, but it's still functional. Even field stripping it is almost identical. You get about 4 magazines of 18 BB's per CO2 cylinder and loading them is easy. The only thing I'll fault it for is accuracy. It shoots about minute of tin can at 7 yards or so. It's not terrible, but it's definitely not a tackdriver either. It's a full blowback pistol and recoil feels about like a .25 ACP and the trigger pull is very similar to an actual Glock.
The Gen5 is more accurate and seems to hit a little harder, but it's actually a double action trigger. The trigger pull is significantly longer and heavier than on the real deal. When you first get your magazines the trigger is incredibly stiff. Lubing the belt helps significantly, as does shooting it and manually advancing the belt. As it wears in it gets significantly better, but it's still a terrible trigger. Since the trigger is actually advancing the belt as you pull it anything you can do to reduce friction and drag on the belt also reduces trigger pull. I rubbed the entire belt down with moly grease and that helped a lot. I also use a small stick or ballpoint pen to seat the pellets in the belt so that they do not rub and cause drag. You get 21 shots per magazine and you need to count them or you'll end up dry firing and wasting CO2. There is no last round bolt hold open and racking the slide does not chamber a round. It also does not field strip like a Glock. The Gen5 is heavier than the Gen4 and it's weight distribution is more correct. The first couple of shots from it deliver a surprising kick and report, but if you continue to shoot it quickly it will kick and bark less with every shot. Give it 30 seconds in between shots and it will be more consistent. The Gen4 seems to be much more consistent. Accuracy is about minute of can at 15-20 yards if you can control the trigger and you'll get just over 2 magazines of pellets per CO2 cylinder. Loading the magazines is also more difficult and time consuming than with the Gen4.
Overall, they're both decent guns, but I feel that the Gen4 is just the more useful of the two. It's function is close enough to that of an actual Glock to make it an excellent training aid.
