your question is contradictory to me....
initially you said that your priority is performance on cng and overall reliability..from which i gather that you want a car which is low maintenance and is not costly.....then you are talking of a swap? swap means more expense plus related maintenance. and lol...1nz-fe is the smaller engine right...so why go backwards? u can get the smaller vitz to begin with...cant you?
so you have to decide yourself first...what is your priority to begin with?
if i were you...i would pick the vitz over the 95 corolla. the reason being...that you cant really compare an 11 year old car with a relatively new one. the only downside to vitz is the expensive parts.....if you can find a hookup for its parts (i think storm posted some really cheap maintenance prices too recently somewhere)...you are good to go.