Hmm... So many guns - so little time. Well, this is a Kel-tec site and pretty much nothing is easier to carry than a P3AT. If you are planning to carry frequently, it is a very good choice, especially, depending on climate, if you don't want to wear a cover garment all the time as often needed to conceal a bigger gun. The P3AT can easily be slipped into a pocket holster and it can also do duty for home defense.
The Hi Point would not be my choice in a concealed carry weapon. For starters it is relatively large and heavy. Secondly, I don't want to carry a single action pistol with just some cheesy little safety between me and an acidental discharge. I prefer double action pistols for concealed carry. I'm not dissing the Hi Point. They are cheap, solid and generally reliable guns with a lifetime warranty and excellent customer service, and like Kel-tec, they are American made. They are simply not concealed carry guns.
Finally, $225 is no bargain for a used P3AT. Brand new ones range from $200 - $300, depending on the finish and local market. A blued can even be found as low as $200 in some times and places. FWIW, I much prefer the hard chrome finish - well worth the few extra $, IMHO.
If you are considering 9mm, you won't find a smaller, lighter one than the PF9. It too can be pocket carried although I personally find it just a bit much to pocket carry for extended periods. However, many here do so. Compared to most 9mm guns, it is easily concealed/carried in a inside the waistband holster. It would also make a better home defense weapon than the P3AT. Frankly, eventually, you need both.
As JFB said, neither of these guns are often highly recommended here as a first gun. The power to weight/size ratio is such that they are not the easiest guns to shoot. The relatively long, double action trigger also serves as the safety and it requires some practice to shoot well. The short sight radius and rudimentary sights, especially on the P3AT also ups the skill level to shoot well. Typically for a new shooter, I like to recommend a revolver, but is sounds like you had no trouble with the P3AT you shot, except that you probably hit the mag release inadvertenly. A slight adjustment in grip and some practice generally solves that. The mag catch can also be filed down a bit.