On a Friday in June I'll be leaving Oban at about 10:00am and need to arrive in Glasgow around 4:00pm. According to Google maps I have 2 options; The A82 is slightly faster at 2 hours 18 minutes while the A84 is about 2 hours 35 minutes. Since I've got plenty of time, is one of these routes more scenic than the other with places I may want to stop? *the A84 does take me through Stirling but I won't be visiting there on this drive.
The A84 takes you to the M9 motorway just before Stirling. Follow the signs for Edinburgh and Glasgow. After a few miles the M9 to Edinburgh splits off to the left. Stay straight and you will be on the M80 motorway to Glasgow which will lead on to the M8 motorway in Glasgow city centre. It will be busy here at 4pm on a Friday.
I prefer the A84 (initially A85 from Crianlarich and then start of A84 at Lochearnhead). I find it more scenic. Kilmahog at the lower end of Loch Lubnaig has a woollen mill and the next town, Callander is an interesting place to stop. You then have Doune which has a castle with Outlander and Monty Python connections.
The A82 will take you by Loch Lomond and eventually into central Glasgow but is a busier road. After Dumbarton there is a junction for Erskine Bridge (M898) which leads on to the M8 passing Glasgow Airport and on to the city centre. This is from the opposite direction of the M80 route mentioned above and also busy.