having had both,
the st is miles better in terms of reliability, refinement (its a hatch back so not beemer quality) and as a complete package and day to day car the st is better, and there a bargain at the moment,
however, they need to following as a minimum to enjoy.,
st170 300mm front breaks,
powerflex engine mount bushes,
decent tires,
eibach spring ( there a ford part number )
and the usual decat, flex pipe remap and filter.
this will give you a decent 170bhp to play with., and they will sit all over a clio on any road,
how ever, the boxes are weak, and like to smach the diffs through the casing, they also pop out of second gear, but its a lovely box, and with a raised rev limit they screaaaaam. w**k on fuel, averaged 24 mpg.
the clio, is quicker, gear box is nasty, breaks are poo. ( every one on here who says you dont need 4 pots or brembos on a road car, obviously have never drove one ) the car seems to undress is self of trim and electrical items, driving position is poo aswell.
both good cars, the clio is quicker out the box, the fiesta is a nicer car.