We've had 3 different people carriers, MPV's whatever you want to call them.
A MK1 scenic on a 99 plate, a Seat Alhambra on a 55 plate and now an 08 Mazda 5.
Not like for like I know and not a Grand Scenic, but the Renault ws the least reliable of the three. Bought 2nd hand with only 30,000 miles it was recovered twice after letting us down completely and had all the instrument panel replaced after a fault (good job it came with a decent warranty)
The Alhambra gave us trouble with the
and air conditioning, but the Mazda hasn't missed a beat.
On balance the Renault was the most comfortable of the three, but we wouldn't swap our Mazda for another Scenic. It has sliding rear doors which are invaluable with our kids in car seats, fold away occasional use seats in boot and a enviable reputation for reliability.
All our ours have been autos and it has by far the best gearbox. The only downside its some of the plastics, whist neat and tidy are a bit plain, we can live with that.
At the end of the day all cars will have their pros and cons, you just need to weigh them up, for my money I'd have another Mazda before I bought another Renault.