The only thing youd notice from the drivers seat of an older Phase1 Clio is the relative lack of soundproofing and the older-looking heater switches. There are other minor differences both inside and out, but if youre moving up to a 16V its all be nicer stuff than you have on your 1.2 anyway.
I went from a 1995 1.2 to a 1994 16V and now to a 1993 Phase1 Williams. Both the 16V and Williams are a lot different from the base models - much more so than a 182 is over a Dynamique 1.2 these days. The step up from my old 1.2 to the Valver was astonishing - handling, weight of the steering, accleration, comfort. For me, the Williams was more of a lateral move with a focus on performance at the expense of a little comfort and spec (no sunroof, manual mirrors, more noisy etc).
Im afraid its unusual that a ten year old hot hatch would be as reliable as a 1.2 base car. To be fair, my Williams has given me very little trouble, but my 16V required a lot more TLC. Im used to it now, but dont be surprised to find bills for £2-500 a few times a year (wheel bearings, alternator etc) - you need good cashflow to look after a 16V.