I've continued doing research on this one. I have found it isn't an easy answer. Even went back to long posts back in 2015 about it. Exchange usually means an online Exchange that does trading, so maybe Exchange wasn't right word. There can be an online wallet, but not necessarily an exchange for trading. I do realize this. Probably didn't explain it well when I used the word Exchange in the title. I also realize there are posts about choosing wallets and other conversations. When I see a ton of posts from say 2015, I am curious to what the updates are since a lot can change in 3 years, but it's still good to read through them. I think from reading if I'm going to join an exchange or oneline wallet or both, maybe coinbase is really the one for me. I know a lot of people are against it, but I think I would use it mostly for temporary storage and then in the future if I ever do get into trading then I can use that too.
For choosing an exchange to buy bitcoin, make sure you it will not give you a less hassle method on the process and you are fine the fees. If you found Coinbase fits your criteria then it's nothing wrong to used them. Im storing some at Coinbase too but not that much. Also have some funds at other online exchanges like here in our local exchanger. If you have local exchanger there in your country, try to check if first before using global exchanges.
For trading purposes, obviously it's mandatory that we need to put funds on that platform. Yes it's risky but we can't do trades regularly if we don't used online trading platform. Coinbase also have some selling option but you are dealing trades directly to their wallet and you will faced their own sell rates unlike in the usual trading platforms.
