Originally the plan was to go for a test ride on the two new GS models about two weeks ago. Unfortunately it was cold and raining heavily on the day, and since I had no proper riding gear I decided to delay it until the weather was more suitable. The last chance to ride them was last Friday afternoon.Unfortunately there was a half-hour delay due to an accident on the route to the bike shop, so I arrived just before closing time. The owner was helpful, and stayed for at least an hour after closing time. After dry and warm conditions all day it started raining just as I arrived at the bike shop, and it rained persistently during both rides. This time I borrowed some riding gear, except for boots, but not all of it was waterproof.The ride was to be on unfamiliar roads, without the curves and bends and hills that I normally ride. And with newly wetted pavement there was no option but to take it easy and not try out the limits of roadholding or handling. Both bikes had about 120km on the odometers, but there was no request to keep the revs under a fixed limit. But the F650 engine apparently had some problems that they had not yet located or solved.Due to other commitments I haven't been able to note down my impressions until 3 days after the ride. So please do not base a buying decision entirely on possibly faulty memories of the rides. Also due to the weather and the late arrival the rides were rather short. About 30km each.The F800GS was ready when I arrived, so I rode that one first. It was fitted with the low seat since my legs are not quite long enough to feel comfortable on the standard seat. With the low seat I could just reach the ground with the toes of both feet.The 800 has wide bars and a seating position which is comfortable for me. No need for bar risers or higher or lower pegs. But the seat itself is not the most comfortable. The bike is very stable, even at 150km/h (on a closed road, of course), which was the highest speed I tried. Loss of licence can happen at lower speeds if you get caught. The front brakes (with ABS) were good, although there was considerable dive at maximum braking. The ABS did not activate. The suspension is very pliant, and bumps were not a problem. I didn't get a chance to check or change the settings, but the preload was set to minimum. Also, I didn't check the tyre pressures.Several have commented about the mounting of the front brake reservoir. It looks silly, and it vibrates and moves around when riding. Apparently a solution is available, but not from BMW.There was very little vibration, either through the bars or through the pegs. I did not find any speed at which the vibrations were annoying or intrusive. The mirrors stayed clear at all times, although their shape and location could have been better. The power felt fairly linear, but was best over about 4,500 rpm.Next came a slightly longer ride on the F650GS, since that is the bike I have tentatively ordered.My memory may be faulty, but I think the 650 had higher gearing than the 800. It was at only about 4200 rpm at 120 km/h. Unfortunately this is just below where the 650 engine power really comes on. This could have been a fault with the particular bike, and may improve with more mileage. This one also had a fault that others have noted. It stalled once when slowing down for a slow turn. It was supposed to have the latest software installed, so it seems BMW have not entirely solved this problem.The 650 had noticeably lower power than the 800, but it was mostly below about 5000rpm. I thought it was supposed to have more low-rev power, but it didn't on this particular bike.With less fork travel the 650 had less front end dive under braking than the 800. But the brakes did not feel as powerful, either. They were capable of a fast stop, but not as easily as the 800.The standard seat did not feel much more comfortable than the low seat.The 650 has faster turn-in than the 800, presumably due to the larger front wheel on the 800. I didn't see any steering damper on either bike, like the ones the F800S and ST have. When trying to steer alternately left and right while riding at about 80 km/h it felt as if it would have been easy to introduce a speed wobble. Perhaps a steering damper would be an added safety feature on the 650. Apart from this, the bike felt very stable on turns.The 650 has a smaller screen than the 800, but for my body length and seating position the wind noise level was lower on the 650. Perhaps because my head was in cleaner air than on the 800. I would probably choose the 650 windscreen for the 800, or a larger after-market windscreen for more protection.Tight turning is not a problem, and the bikes do not feel as top heavy as the 1200GS. Obviously with my short legs the 650GS is easier for me to get off the side stand and to a vertical position.Before even seeing the bikes I had put my name down for one of the first 650s to arrive in New Zealand. After an initial test ride of insufficient length and in adverse conditions my preference for the 650 is unchanged, but with a few reservations. The main reasons for choosing the 650 was the lower seat height, the cast wheels with tubeless tyres, the lower price, and the earlier delivery. The reservations are that BMW will have to solve the problem with stalling and the low power below about 5000 rpm. I will go for a test ride when I get home and the 650s become available there for test riding, and will delay delivery of a bike until later in the year when the problems have been identified and solved.The 650 would be a satisfactory and adequate substitute for the 1200GS, but I will try to keep the 1200 for longer rides if possible. The lower weight of the 650 is certainly noticeable, and would be an advantage on gravel road rides. I would probably change the gearing, to make it more suitable for the 100 km/h speed limit, with 100 km/h corresponding to about 4500 rpm. That would still give a potential top speed over 200 km/h.Sorry, no photos.