1) All things being equal, it takes more skill to be consistently accurate with a pistol than with a rifle - the rifle having the benefit of a longer sight radius (or optics) and the inherent stability that comes with a stocked firearm. (Not to mention the weight-to-trigger pull ratio disparity with a pistol).
2) Unless you are a rifleman deployed on the battlefield, you are going to spend the lion's share of your time armed with a pistol. Walking through the local supermarket with a rifle slung across your chest tends to get the locals excited.
3) Pistols fire a relatively weak projectile compared to rifles in general and thusly, may require more follow-on hits to get the job done; making recoil management, sight tracking and reload skills a must.
Here are some of the key training factors I always try to hit on every time I train:
1) Engagement speed. In it's purest form, this is recording the time it takes you to draw your pistol and place a round in the effective zone of your target. I like to rotate between a paper target, like an IPSC/IDPA, and a C-zone size steel, like the one pictured above.
Like I pointed out earlier, we don't usually walk through town with a rifle slung, likewise most people carry their pistol concealed; therefore, you should do most of your drills from a concealed draw. Granted, I will be faster on target with an exposed belt holster or thigh rig, but if you don't spend some quality time practicing clearing that cover shirt , you are setting yourself up for some real world failure.
They way I usually run this is: Set up at the 10 meter line facing an IPSC or C zone steel (steel has a 20 degree down angle to prevent return fire), arms naturally at sides (you can mix it up and do it from the surrender or while holding something else in your hands - like a cup of coffee and a magazine). On the buzzer, draw for one hit. With an overt holster I try to keep my time at 1.00 second or less (I can generally stay around .90). For concealed carry, try to keep it under 1.50 (my last run was 1.22).
2) Multiple targets. If you aren't regularly practicing multiples you are leaving a large hole in your skill set. (Your odds of facing groups of attackers is only going to grow as our society decays - in my opinion at least.) These types of drills will really give your eye muscles a workout as they have to make rapid and multiple focal transitions. The El Presidente drill is a well proven tool for this (or a Vice Prez if you want to conserve ammo). What I have found to be a good technique is; after you have made your first shot, your eyes will be focused on your front sight. As you begin to shift to the next target, you will lead with your eyes (the pistol actually trailing slightly behind) shift your focus to the next target and when the pistol "shows up", shift back to a front sight focus.....repeat process until finished. The transition period I just described only occurs in maybe a second, but a key training point to remember is to start slow and deliberate, making sure to get the whole process down....then start pushing the speed. Your goal is to shoot an El Prez in under 10 seconds, all A zone hits. Another aspect of training for multiples is to change up the order....shoot them left to right - right to left - center and out - back and forth. Since in real life you will need to assess the most prominent threats and assign a quick threat hierarchy, engaging the closest and/or most dangerous first.
3) Accuracy. There are many really good drills for developing accuracy, like the 700 Aggregate and Dot Torture. One that I use frequently is this: Shooting at an IPSC or C zone steel (works best with steel due to the distances involved), walk to the 15 meter line, fire for one hit - strong hand only, transfer to support hand - one hit, freestyle - one hit (you must achieve a hit on the steel before moving to the next hand). 25 meter line - same thing. 50 meters - same thing. 75 meters - same. 100 meters - same. Most shooters find this a rather daunting drill, but give it a chance - those distance shots really teach you to develop your sight alignment and trust your sights. This drill can net you some big gains in the accuracy department. Keep a log as you do this drill and record how many shots you needed to get your hit at each station. As your number of dropped shots decreases, start to add some time constraints to the drill.
4) Manipulation Skills - In Particular, Reloads. My favorite drill for this by far is the 3-3-3 drill. I like to shoot this from the 10 meter and the 25 meter line. You set up at the 10 with three magazines of three rounds each. One mag loaded and the other two in their mag pouches. On the buzzer, draw shoot three on steel, reload, shoot three, reload, shoot three. All rounds need to hit for time to count. You want to try to keep it under 10 seconds. If you go on Youtube you can find Kyle Lamb (SGM, Ret.) shooting this drill (I think he calls it the "Reload drill") in 6.41 seconds. My best time is 5.52 seconds.....although I have a sneaking suspicion that Kyle could smoke my time if he really tried. When I shoot this drill from the 25 meter line, it usually increases my time by at least 50%.....which brings up another good topic - you need to apply the right amount of gas for the right amount of distance.
5) Shooting On The Move. This is another important one that I rarely see people training on.....and when I do see it, they are shooting while walking straight towards the target. I understand there could be a legitimate reason to close the gap straight on with your target - but in most cases, we move while shooting to make ourselves a harder target to hit. Moving straight towards an active shooter does not make us harder to hit (in point of fact, we become a perceptually larger target)....moving laterally does. It takes a fair amount of practice to get good at shooting on the move, which is why I always make time for it. The technique, in a nutshell, boils down to - using your lower body to absorb the "up/down" action normally present when we walk; and keeping your elbows slightly flexed to help mitigate any negative torso movement. I tell students - walk like you would if you were holding a full-to-the-brim cup of scalding hot coffee. Try walking lateral to the target at the 15 meter line while engaging. Many shooters will get the "strobe" effect when they first try this....walking until they actually break the shot at which time they basically stop moving. Try to avoid this. Start with a slow, consistent pace and as your hits improve, quicken your pace.
This is by no means exhaustive, but represents the cornerstone of a good training regimen. Adding malfunction drills, shooting from cover, positional shooting, rhythm drills, stress fire and wounded shooter drills can also be of great benefit.