its Binance for me. Not just for alts alone but for all round service and satisfaction in key areas like this
1. It has an air tight security and even if there's some sort of hack (which financial platforms are always susceptible to), funds are safu.
2. Service fees for withdrawals on both eth and btc are cheap
3. The fact that one can now directly convert busd or btw to ones local currency as well as buy with his local currency makes Binance the most complete exchange for me