I can only give a brief review of the Howa 1500 mini action, as I haven't handled a T3x. The Howa mini action is small and easy handling, as its receiver is even shorter than a short/standard (308 Win length) action. I believe it only comes chambered in 223 Rem, 350 Legend, or 7.62x39mm. Anything longer won't fit. This also means it uses its own mini length magazines, which hold 10 rounds of 223, and cannot use the other Howa 1500 mags. Rounds fed flawlessly from the mags (I bought an extra; it came with one), and casings ejected nicely. Price was right as I bought it last year on sale from Bullseye North, a CGN advertiser, for $640. Barrel is medium profile and comes threaded and capped with a thread protector. It uses commonly available Remington 700 pattern scope bases.
Now the cons. Lots of cheap feeling plastic parts, including magazines, trigger, trigger guard, and mag release tab. The mag release tab was sharp enough to cut my finger. I rounded off the edges and it's much better now. The tab also needed a break in, as it wouldn't lock mags in without a firm tap on the mag bases. After a couple dozen forceful mag seatings, it now seats mags with a gentle insertion. Stock is fairly beefy, has metal sling studs, but it touches the barrel. Bolt handle knob is hollowed out and the hole edges are a bit sharp. The bolt felt stiff out of the box even after a cleaning and light oil coat. It did eventually work in and is now smooth cycling. Accuracy was mediocre at first. It didn't seem to like any factory ammunition I fed it. After about a hundred rounds, it started settling in and favors a couple types of ammo; getting about 1" to 1.5" five shot groups at 100 yards.
Overall, once broken in, it's a reliable and affordable range plinker or varmint rifle. If I could setup a table and chair to knock off gophers, I would probably pick a more accurate heavy barrel rifle. But the Howa mini action would be good for knocking off coyotes in a wooded area, or an affordable day ringing gongs or breaking clays on the berm.