One of the major benefits of kegging over bottling is how easy a 5 gallon keg is to clean. Mini kegs are just big bottles. You still have to clean them, and they're tough to clean.
Corny kegs are tough, You only need to occasionally change the o-rings. Mini-kegs aren't nearly as strong and you need to get new bungs more often.
Force carbing is easy with corny kegs. Mini kegs still require carbing with sugar, and there's lots of threads on this site about deformed, leaky, or exploding mini kegs.
You can get CO2 tanks easily at a welding supply shop and swap them out, just like a propane tank. Mini kegs use a proprietary CO2 system.
You don't have to go big and build a giant, 5 tap keezer. A small fridge, a used corny keg off craigslist, and a conversion kit from online and you'll be golden.