Hi Rachie
I worked for MYT last summer and thoroughly enjoyed my time with the company - it was brilliant!
I have been asked back this summer and am facing a dilemma having to choose between Britannia and MYT. Britannia would offer me the best career prospects at the particular base that I would be located, but unfortunately the salary is quite a bit lower (enough to make a difference to my finances/outgoings (even taking into consideration the higher flight allowance with Britannia)).
Your long term prospects may or may not be better with MYT but you will still gain valuable experience and hopefully be asked back the following year (or you can always apply to other airlines afterwards).
Although I am still considering my options, I will always think very highly of my time with the company and have many fond memories from last year! I am sure that you will also have a great time - please don't be put off!