One of the most gym-knowledgeable (and best built) guys I've met said: "The best workout is the one you're not doing."
It's probably the truest and smartest thing I ever heard in the gym.
Whatever you do, DON'T GET IN A RUT. The body is an amazingly adaptable machine. In a week or two, your nervous system will adapt to a routine and perform it with the minimal stress. Minimal stress = minimal muscle damage. Minimal muscle damage = minimal growth.
Don't get too hung up on a routine. There are thousands of em out there and everyone has its promoters. They are all right. And they are all wrong. You are different from every other person on the planet. You are also a different person every single time you step in to that gym.
So... make a routine. Whatever. Frankly it doesn't matter. Just pick one. But my advice:
1) Instead of "occasionally" shocking the system. Do that every workout -- every exercise. For this, you may want to do a different exercise every time you hit a body part. There are a ton of em out there on the net for each body part. Try em all. If one works, stick with it for a while, but always keep the body guessing.
2) Change your "routine" completely every 2/3 months. During those 2/3 months, keep changing the order of exercises, the exercises themselves, even rep/set/weight ratios counts (e.g. high reps/light weights vs low reps/heavy weights.
3) Looking at your body type, try to keep the lifting time under an hour. I'm similar, and I try to keep my lifting time to 40/45 minutes max. I spend another 30 minutes doing yoga/stretching/core strength stuff. I don't do cardio cause it never struck me as very efficient (diet is the big stick for body composition in my view, with cardio as fine tuning). I prefer having fun on a hike or on a bike -- you get a lot more out of those things than just burning some amount of calories that you just could have more easily avoided by not ingesting them in the first place. Your mileage will vary. You might really enjoy cardio. You might chat a lot more than me, so your 90 minutes could equal my 40.
As for the full body versus splits, there's no right answer here either. Try them both -- constantly. The only rule of thumb I use is that for newbies in the gym, full body is always safer cause a novice is much less liable to get too sore (from focusing all their energy on a particular body part), and hurt themselves or quit. Once you're no longer a novice, there's advantages to both, so why limit yourself. Everyone should try some variant of HIT or HST at some point (both are full body, one work set only-type routines).
You're going to hear a lot of people who are sure of one thing or another on this thread. Listen to them all. They are all right. But they're also all wrong. Myself included
And just to head off some comments, no, I don't mean routines are worthless, or that there aren't bad ones for you. A full body workout with 5 work sets for each body part 7 days a week is probably bad for 99% of people that aren't injecting gallons of illegal substances. In my view, the most common mistake in designing a "routine" is to neglect rest. I find there's this weird value system that says someone who works out 6 days a week is obviously more advanced than someone who works out 3. Which is crap. People are always asking me the number of days/week I work out. RJ.com did too. I honestly don't see what the hell that number tells anyone. It's just like height and weight. Both meaningless in isolation.
Uh, I guess that turned into a rant.
Damn. My drugs wore off.