Well firstly i have yet to hear of the CAA ever grounding a mon aircraft for not being airworthy, a jet 2 757 was recently, thats not rumour its fact
Secondly ive flown with both operators numerous times with the job and mon are in a without doubt better, the aircraft cabins are in great shape and they appear not to be held together with gaffer tape as jet 2 are, the toilets seem to work as opposed to jet 2 who it seems allways have at least one toilet inop
Thirdly ive yet to suffer a technical delay with monarch and they always appear to leave on schedule, in stark contrast to jet 2 who seem to suffer endless delays, and the on time stats appear to back this up
Finally the on board service is generally of a far higher standard
To sum up, if jet 2 were a town it would be called stockport.