tft & sheild

are this sheild ( compatible with 3.2" tft touchscreen ? if yes, are compatible with arduino mega?

Possibly. It rather depends on which 3.2" tft screen you are talking about. I have seen one with a 2x20pin connector which should fit, and this board looks like it is quiet configurable. The board is clearly made for Uno but will fit on a Mega just like any other Uno board. This is just as well, since there wouldn't be many pins left over if it was used on a Uno. If you are half-way smart, you would get the shield and display together and ensure it is made for Mega in the first place. It will probably be cheaper too.

Is this sheild ( )better, because it contains a number more of pins?

That board is clearly made to fit on a Mega. It uses the pins at the end of the board, thereby not hijacking the pins you would normally use for other purposes. It looks similar to the board sold with the Sainsmart display.

Thanks a lot