Another notable difference between AW and WoT is the garage slots. In WoT you need to pay gold to unlock more garage slots, but in AW those slots are free.
There isn't really a need to sell tanks in AW once you're done grinding them (or just don't want to play them anymore) to free up your garage slots, and in fact it is generally better to keep all of the tanks you buy because each additional tank you have gives a small bonus to the amount of XP you earn in matches (there are diminishing returns starting at +20% XP, but you should still be able to get it over +25% if you buy enough progression vehicles and manage to collect a few premiums).