I have flown weekly with BMI since September. They seem to have far fewer cabin crew than BA (as few as 3 on some domestic routes) but never have I felt less safe. In fact their generally higher energy levels and apparent pride in their job would mean I would have no concerns about their ability to cope with a fire or similar.

Of course I prefer to have more cabin crew. Which passenger wouldn't? I still miss the purser from the UD on BA longhaul. But I don't think that safety takes a hit in these cases.