The Diana 34 is an awesome spring gun with more Power than the HW30s. In my opinion this power is wasted if the primary purpose is plinking. More power usually equates to more hold sensitivity and more difficulty shooting.
The HW30/Beeman R7 sort of hits that perfect spot. It is crazy easy to cock, very quiet, very smooth, is very easy to shoot and is very accurate. It will pest in a pinch as well.
Both the Diana and the HW are leaps and bounds better in most tangible ways then the Crosman. I don't have any first hand experience with Hatsan.
Best advice I can give is don't get hung up on velocity. We are Americans. We have real guns for that.
. A nice low to mid powered spring gun is a thing of joy.
If it were me and I could only have one air rifle it would be one of my HW30s, probably one off the 177s.
Admittedly this was only around 10m but I was still very happy with this. My HW30s's all shoot fantastically out to about 35m or so but at about 40m my skill drops off considerably with spring guns. I do have an HW97 that makes me look pretty good at 50 yards.
HW30s 10m 6 shots, pellet for scale