Hi all. I have had both of these for a good number of years and become pretty much expert in their use and their inner workings.
I would have no hesitation in choosing the HW75.
Ive been involved in more than 1 or 2 of these pistol field target side shoots too, where again i would recommend the 75.
Both are beautifully made but the accuracy of the HW45 off hand is NOT as good as many would have us believe. I think maybe its power, looks and quality lead many to assume it is very accurate, or simply exaggerate because they are so fond of it. I will post some offhand and benched comparison results. Also pellet recommendations if anyone would like them. The real problem with the 45 is controlling the recoil, which serves to throw the gun slightly top heavy. I have carefully studied the movement through the fitting of a rifle scope and even built a small wooden rig to detect its movements in the hope i might be able to tune them out a little.
For the record there is slide rearward buck into the hand, followed a milli second later by a slight leap forward and upward by approx 1/4" There is also a very detectable anti clockwise twist as the spring unwinds clockwise but travelling in reverse of course.
I have noticed that your field target members are having trouble controlling it which does not suprise me. I have a few small tuning recommendations but its pretty much there from a design point of view.
On the other hand, the 75 delivers no noticeable recoil from its hammer or the valve release, with barely 3mm of upward movement from the pellet/air release from the end of barrel. Bench rigged it has the potential to virtually same hole at 10m, while i have managed comfortable 3/4 inch groups and less off hand.
Its light on power in comparison but can be improved a little but can still drop std field targets out to 18yds.