It is very not advisable to move cryptocurrencies between exchanges unless perhaps for bitcoin in order to save on fees.
Fees for XLM transfers are negligible, so it’s best to withdraw to own private wallet first before depositing to another exchange. Transfers to/from good exchanges should just takes seconds each way.
That way u can move a small amount of Lumens as a test before trying with a big one.
That way, should any exchange have trouble, then you would only need to deal with one, instead of two at the same time.
A good guide on these exchanges nevertheless.
