In my personal experience as a non-law enforcement firearm carrier (concealed handgun licensee) over the last several years I have learned some key pieces of knowledge, out of necessity, to ensure my safety and comfort, as well as to those around me. In my job I have no restriction as to my CHL and therefore carry daily, being that my job also takes me outside for the majority of the time, and that I'm not in a constant sitting or standing position, comfort and adaptability have become integral in my clothing and holstering decisions.
I have carried everything from a J-Frame Smith and Wesson revolver to a Glock 17 daily, and I have found that no matter what I carry, the firearm I choose is subjected to high levels of moisture being under clothing, and against the body with little breathing room. These conditions led to the pitting and rusting of many of my guns, to which I had to clean and oil nightly. I have since changed over to only carrying Glock firearms as a result of the following facts: 1. The tennifer and steel combination they have designed has such a high level of rust resistance that after seeing the torture testing it is almost indisputable as to their resilience. 2. I also like the size of the compacts they produce as it is both easily concealable and still quite accurate and manageable. 3. The Glock is readily supplied with aftermarket options from a drop in trigger job to a full customization of the frame or even replacement with aftermarket frames made of aluminum or titanium. My personal choices have been a slightly lighter trigger pull, with extended slide release, and extended takedown lever; I have found that an extended magazine release causes the magazine to fall out in the course of my daily carry.
I typically prefer to carry outside the waistband as it allows more comfort and accessibility, but do find myself in clothing or situations where I must carry IWB (in the waistband). The largest problem I encounter with holsters is that they put the firearm in a position that causes it to show, whether a full outline or a butt sticking out. Paddle holsters have become my primary holsters, the reason being that they are the easiest to remove rapidly and replace should I have to enter a business or other building where concealed carry is prohibited or restricted. Another factor I consider in holsters goes with the above same condition of sweat and moisture, the majority of produced paddle holsters are injection molded plastic, or vacuum formed plastics, these obviously have great resistance to moisture, and they are extremely cost effective. While I prefer to carry outside the waistband I do find myself carrying IWB a proportionate amount of the time. When I must, the biggest of my concern becomes comfort. I own a variety of IWB holsters including the Fobus design which I will deem the most durable, and least comfortable because of its rigidity and pressure points, but it does allow a consistent draw as it is molded and not effected by moisture. Another style I own is simple leather fitted with steel belt clip; this is much more comfortable as it has much less pressure points or edges and a main footprint. The cost is affordable on these and I have found that unless I fully submerge the holster they are quite durable. I have played with the 'pager pal' and others like it, but they simply don't go well with the type of pants I prefer, but if you wear a baggy-crotched pant you should be alright. I really enjoy a 'tuckable' holster such as the Galco USA as it allows carrying in situations where you must dress nicer, there is nothing worse than being the only guy in a room fully of suits with a polo on. My favorite for daily carry when it comes to IWB is a simple ballistic nylon holster with metal belt clip that works for a variety of guns. There is another holster that I wear quite often in place of an IWB or tuckable, and it is a 'holster shirt'. It is much like a muscle mapping or base layer shirt being tight-fitting, but with a padded shoulder holster molded into the material, this is my preference, as it can be used with a button-up dress shirt and tie and I can leave a top button below the collar open to gain access when needed. Additionally there are holsters on each armpit so there is room for a firearm, knife, extra magazine, cash, whatever.
My biggest suggestion for choosing a firearm and holster is to evaluate the mass of your time spent carrying (including the weather, your clothing preference, your personal threat level, etc.) and determine if from that point what is best for you. You might find yourself having to open up to a firearm brand or model you typically don't like, but it is the best for your personal situation. For example, I have been caught in several downpours where if I hadn't been carrying my Glock, I would have caused significant damage to my firearm, and additionally the fact that I had a kydex holster allowed me to dry off the kydex and again avert further damage to both the holster and firearm, whereas a leather magazine carrier would have been severely damaged and cracked after drying.