Both lakes are not great in terms of traffic. I like the northern end of Lake Garda but I see it as a place to settle in a base and then use the ferries to get about rather than the roads. Last time we went we did a fly drive to Verona and the car was mostly used for the airport transfer.
The little harbour area in Malcesine is very nice and a trip on the cable car to Monte Baldo provides great views.
Lake Garda is also more accessible from the Dolomites, compared to Como, as the lesser known Brenta Dolomites are north of Riva del Garda. The smaller Lake Molveno is a quieter destination and the roads quieter.
If you decide to go to Como, the road from Landeck to Como through the River Inn valley, via Zernez & St Moritz is one of my favourites in all of Europe. Stay at the northern end of the lake.