Thats a tough call. A big property that deer can live on year round I like early season, a small property thats a few acres etc, the rut could bring bucks from neighboring properties in. Ive scored on lots of targetted bucks early season, but usually its within the first 2 weeks of the season "if" its going to happen. Targetting a buck early season can sometimes be incredibly predictable especially when bucks are still in velvet, or just out of velvet. But once they shed, the game changes quick, testosterone starts to build up, they no longer tolerate bachelor groups or other bucks quite as much, they start to become more nocturnal, and they start establishing a territory around their bedding areas.
Hunting the rut can be incredible, or heartbreaking. A doe comes walking in with a stud in tow, woohoo, easy cheesy. A hot doe getting chased under your tree or accross a field offering you no shot can be frustrating, but, still cool to see.
For me, I like early season better personally for targetting a specific buck. Bucks arent as pressured, and if you did your homework you should be able to get in close to their bedding areas where they will start making rubs and moving around some in daylight. The rut can also have that buck you are targetting miles away from where you watched him all summer.