I can't make the decision for you, but will try to illustrate my thoughts (which may help you to make your mind up).
It rather depends on what use you see yourself putting the car to, whilst you own it. If it is town (only), then the 1.2 will be all the car you need. If you venture outside the city limits however, the additional grunt will not only make the bigger-engined car a more relaxing cruiser, it will also make for a safer car for overtaking. There shouldn't be much of a fuel consumption difference as the 1.4 will allow you to change up at lower engine speeds.
It is very important to choose the engine which matches your needs - the power (and the way it is delivered) really defines your driving experience, and its worth the effort to get right.
I would also try to get a test drive of both engine sizes - this will assist greatly in helping you choose.
I am quite a late convert to French cars in general, and Renault in particular. A car I had before (which was a great motor) was a Ford Ka Luxury - I owned it from new, and in 3.5 years (and 88,500 miles), it only needed a pair of rear shock absorbers, rear silencer, bulbs, and an HT lead. I fitted larger alloys & tyres, and the car was like a go-cart around corners.
I'm not slagging off the Clio, you understand, but as your first car, its a big step, so try as many as you can to get it right.
Hope that helps.