think im in a good position to comment here having swapped from an R27 to R26.
firstly and the most obvious thing is the extra power which is what actually made me make the swap, its just as fun revving the nuts of the clio, its more accessible, more usable and does put a smile on your face, the R26 in 3rd gear is stunning and id challege anybody who has made the move to say they dont now love the boost! You very quickly get upto silly speeds without realising it!
Steering for me isnt as direct as R27 but i havent really chucked it about due to waiting for new tyres, it certainly aint no slouch thought the corners and i do think it will be better than the clio when i finally get a chance to push on especially as having the LSD!. As people have said it isnt as chuckable as the clio but its not a bad thing IMO it does feel more settled and doesnt hop and jump around as much as my clio did.
either car is awesome, and i sometimes really miss the R27 but having the xtra ooppphh really does appeal to me and its worth testing a R26 before getting a clio!