I've had both sidecars and trailer and done thousands of miles with each including about a thousand miles with my current diesel pulling a two wheeled trailer with a dog in it..
If you don't want to carry a passenger I'd go with a trailer. Sidecars are fun but sap power and kill top speed and most diesels have modest power to start with I certainly wouldn't recommend it for a 10 hp bike. My friend who has studied automotive engineering says that total frontal area of a vehicle is the most important factor of a vehicle drag and hence top speed and with a sidecar you are probably almost doubling that. I've had both sidecars and trailers and have currently retired my sidecar in favour of a two wheeled trailer behind my diesel bike. I use it for commuting to work and every day use. Other advantages to consider are that you're stuck with a sidecar on the bike as there is no real easy way of making them quickly detachable and still maintain correct wheel alignment whereas a trailer can simply be uncoupled or re-attached for each trip. I also have better success parking in my crowded street with the detachable trailer than a sidecar which needs a whole car parking space. I'm not trying to be anti sidecar, I really love owning and using one but this is all in context with a lower powered bike and luggage capacity.
I've had both types of trailer, single and two wheeled. Both are fine and don't adversely affect the bikes handling or speed plus you can still filter through the traffic if you are brave enough, especially with a single wheeled one. You can feel the weight of the one wheeled trailer in much the same way as you can feel the extra weight of full panniers or a well behaved pillion. With the dog in it I could feel when she leaned from left to right in much the same way as a pillion looking over your left shoulder then over the right one. There was also a bit of extra momentum when banking into a fast tight corner but that was pulling it behind a 1200 Bandit so probably dosnt apply here
The two wheeled one has hardly any affect on the bike at all except a lower top speed climbing hills. The flat road top speed is almost unaffected and that is with a large Rottweiler in it
I deliberately put the coupling as close to rear wheel axle height as possible so any push on the bike from the trailer would be neutral and it kind of works as far as I can tell. As for riding style I am more cautious towing than being solo as stopping distances are increased and I hope to never get into a rear wheel skid when banked over with a trailer pushing me into a jackknife as its bound to end in tears.
The only other thing to consider is the trailer coupling bracketery. It has to be strong and rigid. In addition to the push / pull forces of a two wheeled trailer the single wheeled trailer will have torsional forces and if there is any flex at all in the coupling subframe it will coil up like a spring (even just a little bit) and then uncoil, this will tend to somehow start an oscillation with the bike and put you into a weave. I've seen it on my earliest trailer experiment and I've seen it with a friends failed attempt which weaved with almost comical affect. And like any trailer you need to balance the trailer with weight forwards or it will be unstable.
This is my current setup. A two wheeled trailer, used to go to part time workplace three times a week and probably totalling over 200 miles a week.
This is my old single wheeled trailer that I've stopped using in favour of the two wheeled version. At a show last year.
I recently fitted to a friends bike and he is doing just fine with it. This is from last weekends camping doo.
Kubota Z482 which is plodding on with unnerving reliability. Three years so far.
1900 Diesel Bike being rebuilt with better clutch control.
) 
