Hi Wigglewood, Welcome to woodworking

Many of the better routers come with both 1/4 and 1/2 collets. A few of the bigger bits ie for door making, are only available in 1/2". Also important is the horsepower of the router. If you can try to get at least 2 hp so you can handle the bigger routing jobs when needed. Opiewan is correct in saying 1/4 will work fine for most jobs.
Just my opinion

Arnold