I carry a G19 as a daily carry pistol with no issues - but I'm plain clothes LE, so I need as much capacity and shootability as I can get in a pistol that's not overly large. The only thing I would say is, IMHO, nearly unarguable, is that you should get a 9mm pistol - UNLESS you live somewhere that the caliber is restricted or capacity is restricted. The 9mm will do everything you need it to do as a self defense pistol, with lower recoil (ducking before the .45 fans come after me with flamethrowers).
Once you're comfortable with the idea of the 9mm, you have to decide on an action type. The three main action types that are going to be "affordable" are (1) striker fired, (2) Traditional Double Action, and (3) Double Action Only.
-Striker fired pistols do not have an external hammer, and their actions are (generally) partially or fully "cocked" by the action of reciprocating the slide (while loading, or as the slide moves during the firing cycle). The result is these pistols tend to have short, light, consistent trigger pulls - which usually makes them "easier" for new shooters to learn. The down side is these pistols are EASY to shoot, meaning the person who chooses one has to have a DEVOUT attention to keeping their finger AWAY from the trigger until they've made the conscious decision to shoot.
-Traditional Double Action (TDA), AKA Double Action/Single Action (DA/SA) uses an external hammer to strike the firing pin. The hammer is forward during carry, and the first trigger pull has to "cock" the hammer - making the first trigger pull longer and heavier than the typical striker trigger. The slide "cocks" the hammer after the first shot (while reciprocating in the firing cycle) making subsequent shots Single Action - with a trigger pull that is USUALLY shorter and lighter even than striker triggers. The advantage of TDA is the deliberate nature of that first shot. The reason some shooters don't care for them is they actually have to train to be effective with that first long, heavy trigger pull; they have to train to be able to adjust between the long/heavy DA and short/light SA trigger pulls; and they have to pay CLOSE attention to "decocking" the hammer after shooting before reholstering.
-Double Action Only (DAO) pistols are hammer-fired guns that lack the single action feature of TDA - so every shot is long(ish) and heavy(ish). The advantage is these tend to be the most "deliberate" pistols to shoot, the obvious disadvantage that they're also the hardest to shoot well at speed. There are DAO variants, like HK's LEM and Sig's DAK that are more complicated in their guts, but yeild a lighter trigger pull than "regular" DAO pistols, but I don't want to make your eyes bleed.
There are a lot of dynamics here, but, as a RULE OF THUMB, the smaller the pistol, the harder it will be to shoot well, and the less you are likely to practice with it (eeks - did I suggest people actually SHOOT their ccw? Heresy!) Smaller, lighter pistols have shorter, harder to hold onto grips, have shorter sight radius (which tend to increase the effect of sight alignment inaccuracies), and have more recoil. There are some pistols which seem to defy this rule, and many find the G26 to shoot almost as well as the G19, and there are tons of HK fans who swear the P2000sk shoots on par with the P2000. But, once you drop to really small (single stack subcompacts), you're going to see a dramatic drop off in shootability.
If I were in your position, I'd look at the G19 and Sig P320 for striker pistols; the CZ P07 or Sig P2022 for TDA pistols; and the HK P2000 LEM or Sig P250 for DAO pistols. I'd try to find a range where you can rent each of them, and SHOOT them, don't just settle for how they "feel" in your hand. Be prepared to drop $500 or more on the pistol (the P250 might be most affordable of the bunch), this is not a place where you're going to want to skimp. When it comes to firearms, you really do get what you pay for, in most cases...
Let us know if there are any other questions you have that we can help you with, and welcome to P-F!