Well, Ive had both a 16V and a Willy and feel qualified to comment! To be fair, the suspension on both cars is very different than on the normal Mk1 Clios, with four torsion bars and wider tracks. The Willy is in turn quite different from the 16V (certainly a lot more than the 172/Cup/182 variants are over each other). It uses the same shocks with different damping settings, stiffer springs up front, wider front track created not just by the wider wheels, but also the wishbones from a 19 16V and longer driveshafts, with the wider wheels giving a wider track at the rear too. Also has a double-skinned front subframe.
16V: Great handling car, excellent grip and lots of stability. Takes the 205 concept further, in that it wont throw you into a hedge with such ease. It actually handles very differently to the Williams - not that different in terms of character, but the front end definitely has more grip on the Willy. 16V relies on grip all round a bit more: front end doesnt dominate so much. Gets more jittery than the Williams on rough surfaces, but its still the no.2 IMO to the Willy.
Williams: Harsher damping means that the ride height returns quicker to level than in the 16V. Harsher ride in general. The Willy relies on this excellent shock rate to give control when half way through the travel available in the shocks - makes the car quicker. The wider front drags the rest of the car around the corner a lot more than in the 16V. Ive had the back end out, but usually its momentary, as the front takes the weight soon after. The Willy stays in contact with the tarmac more easily with its faster rebound rates and therefore grips very well on uneven sufaces. Blinding car. Given also the flat power delivery and I really have never been in/driven a car that cover the local B-roads so quickly. Leans a lot, but seldom loses grip.
Oh, and dont confuse handling with grip. If a Mk3 Golf (one of the all-time blunders of hot hatch handling) out-handles a 16V (one of the peaches) then theres something not right!¬