Flycat

From Greenock both are doable by train but you would obviously have more time to explore Glasgow. I don’t think you can go direct from Greenock to Edinburgh and would have to change trains in Glasgow to get to Edinburgh. We have done this stop twice (in 2021) one being overnight which obviously gives more options. The first time we didn’t have a lot of time but got the train to Glasgow and did the HOHO bus tour which was excellent. The next time we went to Balloch for Loch Lomond via Glasgow on the train and did a boat trip on the loch once there. The next day we again headed to Glasgow and did a tour of the West End - university area, Kelvingrove Art Gallery & Museum, etc - using the metro system affectionately known as the clockwork orange! If you plan to do something independently there are various options once you get to Glasgow. By the way, there are 2 train stations in Glasgow. The train from Greenock stops at Central but you might need to go to Queen Street if you want to go farther away including Edinburgh but they are only about a 10 minute walk apart.