I’m making a big assumption that this will be your main and only timepiece, if so ask yourself when will you wear it? If you plan to wear it often to work with a suit and you generally dress smart during evenings and weekends, then the 5120 is a good choice. If you dress casual for work, the aquanaut is a good choice.
Personally I’d opt for the aquanaut, but you need to ask yourself under what conditions you’ll be wearing it and what will go better with your dress sense and personality.