Depending on your exposure during residency and the climate of your chosen practice environment post-residency, you can do these cases without a fellowship. Some hyper-competitive markets may require the extra piece of paper on the wall, but if you got the skills and desire to do the procedures I believe they have little to add to the skill set of a well-trained general surgeon.
I did train with some people that went into fellowships because they wanted to LIMIT their future practice to only one area. I guess it may make some sense then. I also know people that did not get adequate exposure in some areas to feel comfortable performing those types of procedures without increased training.
Regarding abdominal surgery, I love laparoscopic surgery and colorectal surgery. I do them both routinely, but not exclusively. Without fellowship training, I perform lap colon resections (including the occasional total proctocolectomy with pouch reconstruction). I do paraesophageal hernias and Nissens. Laparoscopy is my preferred route for the repair of almost all ventral and inguinal hernias. A laparoscopic Graham patch is hard to beat for a perforated peptic ulcer. I perform lap bands and lap gastric bypasses. I perform open colon/rectal resections when necessary as well. In my case, I like the variety and would be bored limiting myself to only one area.
Anyway, the choice really needs to be a personal one. If you want to be limited to colorectal work only then go that way. Most CRS fellowships will give you plenty of experience with laparoscopic colon resections. If you want to do other things, then an MIS fellowship may be better for you.
Regarding MIS fellowships, there is a lot of variability regarding the types of cases you'd be exposed to at any particular location. Some fellowships are heavily (or exclusively) geared towards bariatrics while others may have little to no bariatrics. Much like residencies, there is also a lot of variation regarding your level of autonomy during fellowships. Some places you'll be a junior attending and once your talent is evident you'll do a majority of the cases with little supervision. While other places you'll be treated as an assistant and they'll expect you to learn by observation. Not ideal IMHO. Unfortunately, this can sometimes be hard to ferret out during the interview process.
