On the other hand, having an older supervisor might help you later if they have a strong reputation and can write a good letter of recommendation for you. Since you'll be spending years at this new place with these new people, you may as well spend some money to check it out. In addition to meeting your supervisor, checking out the facilities and environs is important too. You'll be working alongside the people in the lab for some time, so it would be nice to get to meet them and have a chat about how they feel about working in that lab. After visiting a few labs, a decision should naturally emerge from your gut instincts.
All projects have their hiccups and mini-disasters.
It's important at such times to not despair and think that it's somehow a reflection of you. Doing good research is all about persevering through all the problems that can and do go wrong. Experienced researchers are used to this and see project fire-fighting as simply part of the job. If you're not enthusiastic about your research, you'll do a poor job and eventually convince yourself that biology is not for you. You can avoid this by choosing projects you'll be happy doing.