I have had the ball flush valve types and now have a Tetford slide flush type.
I prefer Porcelain to plastic. and full "Oval" sometimes called "Residential" to the round.. in fact I do not like round at all.
THe flush mechnisim is more complex on the tetford.. But ... I have only seen two issues with them over the years (neither with mine) and both were easily fixed (one was a leaky valve. the other a linkage came loose).
On the Ball type flush valve the shaft broke, that was a mel of a hess to fix. Had to take it all apart turn it upside down.. Plus the water valve liked to stick open