ETOPS, every airline in the UK works on the principle of "Captains in waiting" so BA is not unique in that aspect.
Knee Tremblers problem I suspect will hinge around life style issues and of course cash in the bank each month and pension values. Job satisfaction would be better in the LHS but this is not really about which side of the aircraft you sit on, more the whole package on offer up to retirement compared to staying put or comparing other companies.
As I mentioned earlier the loss of the final salary pension was the deal breaker for me, and I think many others in similar circumstances.