A 9mm carbine is definitely easier to shoot accurately than a 9mm pistol, but a carbine with the magazine capacity of a small single-stack CCW pistol takes away one of the big advantages of a carbine for HD, and that is reserve capacity. For a HD long gun in 9mm, 10 rounds is a *very* limited capacity. As a point of reference, my HD pistol holds 18 with flush-fit magazines and 21 with slightly extended mags, which is pretty typical of full-size 9mm's.
If you can afford it, and you like the design OK, an M1 carbine is about twice as powerful as 9mm, and an M1 carbine has 1.5x to 3x the reserve capacity of the Hi-Point.
If you like the M1 carbine but you can't find an affordable one, a Ruger mini-14 in .223 Remington would be another option. Or one of the various 9mm carbines with over-10-round magazines.