Not entirely true, the main reason most fit the 1.7 is because their 1.6 has shat itself. They are well know for big end and head gasket failure. 1.7 is a lot stronger has mls headgasket and coated liners. I've ran mines into the red temperature zone twice and still haven't blown a gasket and that's on 175k miles.
Cheaper to tune aswell I bought frp cams and got it napped for 99 with loads of other small bits and bobs made 160 on sitechs rollers and that cost me less than a grand and was mega reliable.