Not sure on the second part, but the 1080i vs 720
p depends on the TV's native resolution.
If it's an HD ready set with supports 720p/1080i it will probably have a native resolution of 768 (1,366x768 pixels) - a 720p picture will be display as is, but a 1080i picture will need to be downscaled to 768. NOt much point upscaling in the V+ just to be downscaled on the TV!
If it's a 1080p set, then 1080i will def be better.
A better explanation
here.