I was looking at a chart comparing grin and monero on the stackexchange yesterday. Link provided: https://monero.stackexchange.com/questions/11107/what-is-the-difference-between-monero-xmr-and-grin-grin

From the top comment:
The main difference I noticed was grin being considered fairly weak for privacy as it hides historic information and transaction amounts but those can be gathered before a transaction is confirmed (when it's broadcast and in the mempool - as I understand it - perhaps there's a way they'll come up with to obscure this further).

I THINK I'd add an con of the grin community being new and grin coin being fairly new too - I think that's their biggest drawback so far (just the newness, nothing to do with the people).