aircraft size
Although not set in stone , aircraft size could give you some guidance. Generally the 777s , 767 s and 747s do the longer flights and the rest do the shorter flights. I apprecaite that this is a sweeping generalisation but as a general rule , big for long flights , little for short flights.
Although longhaul means constant jet lag , I find that easier to cope with than doing 4-5 early starts in a row. However as someone pointed out , you need a VERY secure other half as for many , their fragile egos can't cope with the possible might happen potential.
It is fab to actually be able to talk to the punters and to spend a few days at your destination as opposed to quick turnarounds .
On the other hand , I would love the odd Rome / Barcelona nightstop.
Not sure which carriers do it but a mixed flying option is the best if the work is 50/50.
Whatever you do , think long and hard and talk to as many crew as you possibly can who are operating for carriers you are likely to work for.