If you have heavy hands there is no reason to waste your time learning anything but straight boxing. 4 oz gloves....Use the saved time to develop a better ground game.
If you weren't blessed with one punch KO power like the majority of fighters, I'd have to go with Muay Thai. the clinch is enormously helpful in MMA. However under K-1 rules, dutch style kickboxing is the obvious pick by a mile. Case in point: Masato vs Buakaw. In an MMA stand up match, Buakaw smashes Masato but under K-1 rules, Masato outpointed Buakaw.