I owned three 5.0 Mustang convertibles..2 '86 GTs and a '91 GT that was modified like crazy. It was in several magazines and was once described as a "Ford Motorsport catalog on 4 wheels". At first I supercharged the 5.0L and then eventually installed a 351 Windsor (that's 5.8L) engine in it and a Griggs Racing suspension, Baer brakes and just about every other modification you could think of. In the end it made close to 500 hp. It was wicked fast and at first I drag raced it, then I road raced it regularly on tracks like Pocono Raceway and Lime Rock. Unfortunately it became more of a race car and it wasn't much fun to drive on the street so I sold it and bought a 2001 Mazda Miata Sport.
I really loved the Miata and while I modified it somewhat and raced it a bit, I drove it all over the East Coast on road trips. IMO it was a blast to drive, even more fun than the Mustang despite the fact that it wasn't as fast it was like driving a go-cart and it felt just like a roller coaster. I drove it down every curvy back road from Nova Scotia to Georgia.
Both cars were toys. I stored them in the garage from November-April and babied them. I modified them and enjoyed them. When I stopped enjoying them I moved on. I sold my Mustang because it became a real hassle to own and drive and bought and loved the Miata for 5 years.
One day I realized that I wasn't driving my Miata much anymore. More than once during a trip I would come to a dead end where the pavement turned to dirt and I wanted to see what was down there. Once I took the Miata down a dirt road, with laughable results. I think that's why I broke the rear control arm. Ouch! I also found that I had gone down just about every mountain back road I could think of. I was getting bored.
I'd always liked Jeeps and I've always owned convertibles. Racing cars was getting expensive and I wanted to try something new. Plus my kids were getting older and we needed a vehicle that would actually function as a "car" rather than a "toy" and could be driven year round, so I bought a 2005 Jeep Wrangler Sport. My intent was to wheel it so I made sure it had the Dana 44 rear axle, 3.73s and put aside money to have it lifted, put skids on it, etc and took it rock crawling with 500 miles on it. At first I kept it stock, with just skids, and then lifted it 4 inches with 33s.
I briefly thought about keeping the Miata because like the OP, I really liked it and hated the idea of giving up on my beloved sports car. I just couldn't afford to insure two vehicles and with the price of used high mileage Jeeps being almost as much as a new one and the Miata needing some maintenance as well I decided that selling it and using it to buy a new Wrangler would be the best option so that's what I did.
So how did that work for me? Well, I was a die hard when it came to sports cars. Speed and handling were the idols I worshipped for almost 2 decades and I traded them in for a slow, rock crawling Jeep. It was a big leap for me in that regards but in some ways it wasn't. For one thing, I found Jeepers to be much nicer people to hang with than either Mustangers or Miata people (the Miata people were the worst!). I joked that I bought a Jeep so I could run over idiots who drove Miatas.
I was always into modifying my sports cars and you can do the same with a Jeep (Just Empty Every Pocket). I found rock crawling to be a lot like racing in that you have to actually have skill and think about what it is you're doing. I found that even though I wasn't driving as fast, I was having just as much fun. I joined a local Jeep club, went out wheeling and best of all, my daughter loved it too and she was my constant wheeling companion and spotter. We went wheeling almost every other weekend and to several Jeep Jamborees and had an awesome time.
And it is damn nice to have a vehicle that you can take everywhere, though everything and not worry. Whether it's exploring trails in the woods, driving through a snowstorm or taking the doors off and the top down and piling my beach chair and/or camping gear in the back, my Jeep can do it all. I'm not worried about it getting scratched or dinged like I did with my pristine sports cars..It's a Jeep! It's supposed to be scratched and get dirty!
Yes it's slow, but for some reason I find it fun to drive. I just sit back and watch the world go by and I was able to sell my Valentine One radar detector and never worry about getting a speeding ticket.
It's a different state of mind driving a Wrangler. These days I'm more into hiking, kayaking and camping so the Jeep is the natural evolution of where I've come to in life. Do I miss the sports cars? Once in awhile, very occasionally I do but I'd never, ever give up my Jeep. If I was going to buy another car I'd get another 2nd generation Miata.
I'm not all that crazy about the newer Mustangs. I was a 5.0L affectionado because just like the TJ 4.0L, it was an easy engine to work on and modify. I don't think I really like any new car. I've been upgrading and maintaining my TJ and I don't plan to buy another vehicle. If I did, it would be another TJ.
As to whether you want to buy a Jeep, think about why you do. Is it to go off-road? Because you want something to drive year round? You won't be getting any better gas mileage, that's for sure. If a convertible is what you want, why not get a convertible Mustang? Saying which is better is the proverbial "apples vs oranges". It's like saying "What's better, wine or beer?" Depends on what you like.
Some pics below shows the evolution of my cars. I'm sticking with the Jeep after 10 years I still love it. It's outlasted the others so that's saying something.