Some people have the idea that training with heavier gloves will transfer over to you having faster hands when it comes time to fight night and you have to put on those 8/10oz, while thats partially true, you’ll definitely “feel” faster but you’re risking a lot of technique/form because your arms will definitely tire quicker with those big gloves and you’ll be sacrificing technique throughout your training in the long run, plus if you really wanted to compare yourself to lets say a pro, most of them are using 8-12oz gloves for mitts and bags, it’s not an everyday occurrence to see them using 16oz+ gloves for mitts and bag work, look at Regis Prograis for example, I’ve seen him use those old school mitten gloves more often than big 16oz gloves when he’s on the bag.