One thing nobody has mentioned thus far is the fact there is no such thing as a 300 amp residential panel.
You will most likely get either 2 - 150 amp panels side by side, or a 200 amp plus a 100 amp panel side by side.
The main difference is the meter can. A 300 amp meter can is very expensive vs a standard 200 amp meter can.
Either way, you have to decide what you will need now, and what it would cost now, vs an upgrade in the future.
If there is any chance you will sell the home in the future you will be wise to consider a larger panel and service
because the future owner will greatly appreciate the room to expand after they move in.
Either way, consult a local, licensed, bonded, Journeyman electrician in your area to go over the fine points
with you BEFORE you decide either way.
Personally, I'd go with the largest service and largest panels I could get, so there would be room for any
additional equipment I would consider adding in the future.
Hope this helps.