Steven,
Personally I prefer the flat glass as it gives a 'true' image that enables you to judge distance better, the convex provides a 'wider' view but things appear further away than they really are.
I too have only started towing this year so would still be classed as a newbie - and like you was a little nervous when I picked the van up in March (however I had towed other trailers in the past) - don't worry 10mins in and you will feel perfectly happy.
Charlie makes a good point - if you can avoid altering your mirror settings when you take them off then it makes life a lot easier when putting them back on.
Good luck and enjoy the new van - we reckon it is an absolutely great van - bags of room, really comfortable, looks great, and tows well.
Cheers
Jon