I was diagnosed at age 12 (just had my 29th "anniversary" two weeks ago). I've been on a pump for almost 14 years and have been on a CGM for a week. Both are from Medtronic Minimed. Even on the pump, keeping my bloodsugars under control is a daily challenge. Not because the pump doesn't work. My sugars just swing pretty wildly. I'm hoping the CGM is going to help me gain better control. I haven't developed any scar tissue from the pump. I just make sure I rotate my sites. I only use my abdomen. I can't imagine not having a pump. It makes my life so much more flexible. I can sleep in, skip a meal, travel to different time zones. It's not perfect - nothing replaces a normal pancreas : ) I am hoping the CGM is going to help me obtain much better control. It's pretty accurate and I'm learning a lot from seeing real time what happens when I am under stress, eat different types of food, etc.
The CGM is really small and it's wireless. You just change the site every three days just like the pump and you attach this little transmitter to it. The pump is a litttle smaller than a deck of cards and most people think its a cell phone.
Sometimes I get tired of wearing the pump, but then I also get tired of checking my bloodsugar, counting carbs, feeling tired from highs and cranky from lows, etc. A few times I've taken a short break from wearing the pump and done shots instead, but I always went back to wearing the pump within a week or so because we control and the flexibility was so much better with the pump. One annoyance with the pump is figuring out where to put it when wearing dresses, bathing suits, etc.
If you are okay with being attached to something (some people just aren't) and you are committed to checking your bloodsugar at least 4 times a day (I test at least 6 times a day) then I recommend you give the pump another try. They are way more advanced than they were 10 years ago. The one I have now actually communicates wirelessly with the CGM and has a lot of other smart features (too many to list). If I were you I would just get both the pump and the CGM at the same time. That will maximize the benefits of being on the pump and you'll just have to go through one period of adjustment rather than two.
A big factor for most people is whether their insurance will cover the pump and the CGM. Most decent insurance will cover it as long as you have approval from your doctor. Medtronic makes it really easy. If you don't have insurance, this stuff costs a fortune - especially the supplies. For example, the CGM sensors are $35 a piece and they advise you to change it every 3 days! Between CGM supplies and pump supplies, the cost is over $750 a month. The pump is over $5,000. I don't know how much the CGM transmitter costs.
Good luck with whatever you decide!