Nothing is guaranteed. That's the first step. If you understand that you aren't guaranteed it then you'll not be setting yourself up for a shock. The conditional offers of those programs are just that. Conditional. Each airline has differing criteria which have to be met throughout training in order to keep that offer and some are more strict than the rest. The same applies to Integrated (Whitetail) courses as if you don't meet the grade throughout your training then I can assure you the likes of easyJet et. al. will lose interest rather quickly!
Despite this though, my tip would be to research each of the schemes individually to see what each of them actually offers you. Yes, granted the majority are MPL licences, however look beyond that to the quality of life post-graduation. Do you wish to work in Europe on the A320 or in the Middle East on the same. If the latter how would you feel given the change of culture in Qatar, for example? I'd also say you need to be realistic given the cost of these courses and think about if you could afford to meet any loan payments on the eventual salary of said airlines. I say this as Eastern European carriers are well-known for paying relative to the cost of living at your eventual bases which translated to Sterling or Euro may not even come close to any loan balance. Finally, do you want short haul, or long-haul? Ultimately putting thought into these will help you make your decision naturally. With this said though, if a scheme that aligns itself to you happens to be open then you'd be silly to not give it a shot as, an offer - despite conditional, is already better than that us Whitetail lot have. Equally, if you don't meet the airline selection criteria you may well qualify for Whitetail anyway.
That's my two cents.