We picked the Marriott Couryard at Graz using Trip Advisor. It is well out of the city, probably you wouln't want to drink drive or get into Old Town at night so use the hotel bar and restaurant they were both friendly and good. The rooms comfortable as may be expected and quiet despite proximity to motorway. Very much a business hotel but nice for that even on holiday. Graz has lovely old town but modern side if you arrive by train looks grotty, stick with it over the river! It took us 45 minutes from town getting lost a couple of times but got back in next morning in 15 mins.

Stayed at this hotel for a company weekend. My only complaint was the distance from Graz but as we weren't paying and only had Monday morning to go in it didn't matter!
Service was excellent, very friendly, nothing too much trouble.
Only had breakfast there but, again, excellent, plenty of everything, cheerful, friendly staff and very high standard of food.
The bathrooms were not up to the standard I would expect in a Marriot but OK, had they been better, would have given an excellent rating.