Mk 3's dont handle as well as a Mk2. However the 16v ABF engine is the best!
Also the Mk3 is more comfortable and generally has more extras like ABS and air-con.
If you want a balls out boy racer go for the Mk2 and spend thousands like Slick (Pedro) on making it go fast!
If you want a good all round car that isnt going to rust out then go for a Mk3.