Compare mk2-mk3, and engine choice?

[vexed]

Last spring i fancied a convertible, so with minimal effort/planning I picked up a mk2 MX5 with the plan of keeping it a few months. I have become utterly besotted with the car and now plan on keeping an MX5. I still find it hard to believe that such a fun car could be had for so little (purchase price and running costs).

I am now wondering whether to stick with what I have- 2004 Mk2.5 1.8. Love the heated leather seats and the lsd!
Or: swap to Mk3 with a 2.0 engine. LSD would be an absolute must. Heated leather would be nice.
I'm not really interested in tuning (although I have considered swapping the anti-roll bars to eliminate a little of the body roll)

Reasons for swapping would be to avoid the rust issue on a car I am planning on keeping more than a year- mine has a little on the sills at the real wheel arch; and the increased power of the 2litre engine.

I love revvy engines- is the 2.0 as revvy? and reliable? Is it still made by mazda or imported from another OEM?
I wouldn't swap for more power if the character of the car and enigne was lost.
Does the mk3 avoid the rusty sills issue?

Thanks in advance for your thoughts!