First of all, welcome to the forums!
If you opt for the Glock, get the "subcompact" G27. It's small and light enough to be carried IWB comfortably (unless you're looking for deep concealment, in that case you need a much smaller gun). It can accept it's larger brothers' magazines, i.e. magazines from G23 and G22. You can buy conversion barrels for your G27 for 9mm or 357 SIG. Glock's .40 caliber magazines can hold 9mm rounds for range use, but you may find that the last round jams. Therefore if you want to convert to a 9mm I suggest you buy some G17, G19, or G26 magazines. You can also put a magazine extender so your pinky finger has a place to rest when holding the pistol. It's a very versatile gun.
If you don't like the Glock's DA trigger (the pull is about 5 lbs, this is A LOT lighter than most DA trigger pulls around the 10 lb range), look into the SIG P239 or P229. SIGs are wider, bigger, and heavier. If you have large hands, you can buy aftermarket grips and install them on your SIGs to increase the width (the Hogue wooden grips are thicker than factory grips, or if you want thinner grips, consider the Hogue extreme aluminum grips). SIG magazines are not as interchangable as Glocks, i.e. P229 magazines doesn't fit in the P239 because the P239 accepts single stack magazines.
Most people want to carry a midsized gun for concealed carry, but wear it a few days and it quickly becomes apparent that it's not feasible (printing issues, heavy weight, cumbersome, etc). You can also consider a Kahr PM9 or PM40 or the S&W J-frame revolvers if you don't mind straying away from auto loaders. Happy hunting!