What size drill motor should I buy?
I am more into features than power.

Most important feature is multi speed function where the trigger is a speed control.
Next is chuck size. Not just max size but also min bit size
Reversible is cool but I don't really use it.
Lastly make is a factor and generally you get what you pay for. On the DIY side drills last years. Just pay the few extra bucks, you will never regret it. But also remember you don't need pro grade that's overkill. 450 sounds ok. I have 3 - 550 watt drills and they are great.