Are the views comparable driving and taking the train from Munich to Garmisch?

Yes, the itinerary through Garmisch is a little more scenic as it involves a (relatively low) Alpine crossing, while the itinerary through Kufstein is trough relatively flat valleys. Fast trains travel through Kufstein; the Garmisch itinerary, without stopping, is maybe an hour longer.

The Garmisch itinerary was once run with direct trains but now involves a forced change in Mittenwald, very simple as the station is tiny, between a German and an Austrian train, each one waiting for the other. Due to a regulatory oversight, the German train is not allowed to run on the Austrian section and vv.

If you want to stop in Garmisch, the town is very scattered and the station is about 15 minutes walking from the city center (Kurpark area), if we want to call it a city center. If you do not want to cope with a PITA factor, you simply stay on the train till Mittenwald and then board the train to Innsbruck. On the Austrian train seat on the right side to see the Inn valley as you slowly descend, clinging to the side of a mountain.

Be informed that between July 11th and 31h, 2016, the Austrian railway between Mittenwald and Innsbruck is closed for maintenance and there a bus service.

It is up to you to decide what you really want. As the Munich airport is well linked to the railway network, there should no need of a chaffeur unless you want really to splurge. Most train connections could happen at München Ost station, without the need to go all the way to the central station.

I have not taken the train from Munich to Garmisch, but the drive is surprisingly dull. Talls trees obscure most of the views, and things don't really start to open up until perhaps the final 20 minutes of the drive. The Autobahn route even runs very close to Starnberger See, but you can't see it.

Thanks. This is very helpful.
I had not realized the change of trains happens at Mittenwald.
I had thought it happened at Garmisch.

Once there was a direct service Munich-Innsbruck via Garmisch and Mittenwald. But due to regulation changes, the Austrian trains are no more allowed over the German section of the line and vv. so now a change in Mittenwald is necessary. Sometimes the time allowed is very strict as they try to keep the same timetable without a change, but it is a cross-platform change - train arrives and you change to a train waiting on the other side of the same platform. If the arriving train is delayed they will likely hold the corresponding train. Hopefully some time the through service will be restored.

Sometimes a change in Garmisch is necessary, sometimes not. It depends on the specific combination of trains.

I just did a search on the Bahn website for August, 2016, for Munich to Innsbruck on regional trains through Garmisch-Partenkirchen. I found a number of direct (ie, no-change) connections and some one-change connections. Of the one-change connections, about half had changes in Garmisch-Partenkirchen, and the rest had changes in Seefeld, Austria. None of the connections were in Mittenwald

All but one Ga-Pa changes were cross-platform; one was a one platform-change.

According to the Bayern Takt wewbsite, there are lockers in the Ga-Pa station, on the side of the station building, next to track 1.

BTW, I can remember times when the train trip between Garmisch-Partenkirchen and Innsbruck did usually required a change of trains in Mittenwald, but this has not always been the case. In 2009, I stopped in Seefeld, Austria, and then took one train from there to Garmisch-Partenkirchen. It's always wise to check with the Bahn schedule webpage to see what the current situation is.