B&S... Thats sort of a difficult question believe it or not. Generally speaking, if you join on the Airbus you will start 330 and from there go 340 to 380. However, as i mentioned before there have been guys held back from 340 and have gone straight 330 to 380 it just all has to do with training and staffing requirements. Same will probably hold true for airbus upgrades before long. Boeing is much simpler, you join on the 777 and upgrade on the 777. As a general rule of thumb you join on a type and stay airbus or boeing and progress as appropriate to the specific fleet. Now the wildcard is they have, on occasion had fleet transfers, but that has only been once in a blue moon and while they "attempt" these transfers in seniority order there are other factors at play. These factors can be anything from not picking up the phone when they decide to call one afternoon to a so called manager not liking the amount of sick calls or "attitude".
As far as command goes, yes the days of quick commands are probably gone. DEC's are here again despite the fact we have lots of very qualified FO's that are being held back because they do not have enough EK time, either on type or at the company. If you do decide EK is right for you than plan on a 7-10 year upgrade and by that time who know's what a/c you will be on.
Not trying to turn you off just being as honest as I can be, good luck.
Cheers,
CR