My sister has 4yo twin girls and she has tried both ways several times....the girls are very close and would love to share a room now but they do keep eachother up and wake eachother for silly things...ie if one needs the toilet or loses a pillow she will wake the other and then my sister has to put 2 back to bed. One of them is not a brilliant sleeper and constantly would disturb the other and the result would be be 2 grumpy bums in the day from lack of sleep. However when they were younger and in cots etc it did work alot better. She hopes to put them back in one room in a year or 2 when hopefully they both sleep through alot better but for now it doesnt work for her. It wont hurt to try they might have no problems with it and suprise you. Goodluck.