Group 1, The Program Followers. These people have their workouts written down to the specifics. The exercises, sets, reps, and weights are all properly programmed sequentially written. If this group of people is following any "half-decent" program they will usually get pretty good results. If it's a program out of Muscle and Fiction, that includes Bicep Blast Friday- It's probably a crock o' turd!
This is usually the smallest group of people in the gym. I would say that maybe 5% of actual gym-goers follow a decent program that has good exercise selection and a logical set/rep scheme. The members of this group usually have worked with a trainer or have adequate knowledge in regards to lifting and they usually have a pretty good b.s. filter on stuff NOT to do in the gym.
Sometimes these programs might be more advanced such as Liner Periodization or a Percentage based set / rep scheme. Other times they might just be basic exercise templates with the exercises, set, reps, and weight based on very little background data or strength testing. As long as there is NO BOSU ball squats, Abductor machine, or 10 drop sets of tricep kickbacks- you might be following a suitable program.
Group 2, The "I feel like doing" group. These people usually walk in the gym, look around the free weight area, do a few arm circles and go right in to ANY exercise they feel like doing that particular day. Maybe they'll do chest (usually the case on Monday), sometimes they'll do arms (very typical on Friday). They hardly every do squats or deadlifts- the main reason they're in the gym is to get their PUMP ON!
This group might spend 45 minutes on their upper chest, 30 on their bicep peak, and 15 on their lower abs. You can almost guarantee that every member from this group does curls in the squat rack!
Group 3, The "Auto-Regulation" group. I really don't know how or why we decide to use a fancy word for this group, I thought instinctive training worked just fine. This group knows what exercises they are going to do, and pretty much has an idea with the set and rep scheme is going to consist of , but nothing is written in stone. They might add in some extra single leg work, or maybe a few sets of chin-ups between a shoulder press. Instead of 3 sets of 5, maybe they decide to hit a few singles because they feel like Killin' it that particular day.
This group usually will stick to the basics, maybe add or take away some assistance lifts, but they are in the gym to get strong and lift heavy. One of the problems with this group is if they feel like killin' it every week, sooner or later they might face "burn out" or end up getting injured. The good thing is that if you're feeling off one day, you can adjust your sets/reps/exercises to fit your energy levels.
There was actually a study done on Auto-Regulation that you can check out HERE.
Based on the study, the Auto-Regulation group increased their bench press and squat more than the the Linear Peridozation group in a 6 week period. Does that make Auto-Regulation superior for every body's exercise goals? Not at all.
So, Which group do you fall under? I hope not Group 2 (that is Jersey Shore wanna be all the way). If you fall under Group 1, and are achieving adequate strength and fitness gains, keep it up. There is no reason to change to the next best thing, unless you feel like you need a break from the program mentally. If you are wondering which program is best for you? I like the advice, "The best program is the one you're NOT doing". Actually that's not fair advice, the best program is challenging, corrects/strengthens your weak links, and produces desired results. That should be common sense.
If you fall in group 3, make sure you base your workouts around the basic movements, focus on getting stronger, and set up a DELOAD week once a month. Limit your workouts to around 45 minutes and perform some single-limb movements as well as having an equal push/pull ratio for upper body.
The best advice I can give is to have a program (GROUP 1), follow it until you feel you mentally and physically need a change. Before you begin your next program go through a few weeks of Instinctive training (GROUP 3), but do so with a purpose and a basic plan. Perform a deload week, then retest your strength in the basic exercises and begin your next program.
Having an efficient well written training program is a valuable component when beginning a strength training and conditioning routine. Keeping track of your progress is very important. However, if you need some time just moving heavy weights based on the way you feel, change things up a bit and get back to going to the gym with some intensity- maybe joining Group 3 for a few weeks isn't a bad idea.