How official is an unofficial offer

[bonesandbakes]

So I got an email from my PI at School A a few weeks ago, telling me I got in. Since then, I've started working with them to plan a visit and they've sent me a funding offer. Then on Friday, I got an email from School B, saying that though this was an unofficial email I'd been approved by the department and the dean for admission. Now if I'm getting an offer from School B, I definitely won't accept at School A (here my research would have to focus on a secondary interest, where I could focus on my primary at School B). Nothing has been paid for yet for my visit to School A, and I feel like I should not go visit now so they don't spend their time and money on me if I'm not going.

My question is, should I trust the unofficial acceptance from School B enough to turn down School A before I get School B's official offer? It might be important to note that School B has a huge endowment, so I don't think it's likely they'll back out at the last minute due to funding.

Thanks in advance for any advice!

[PsyDuck90]

I would visit anyway. This way you know you are making the most informed decision. An unofficial acceptance is usually a green light, but there's always a chance something happens. 

[as2472]

I would also recommend visiting anyway. Even if you don't go, it can help build professional relationships with professors at school A, who will be your future colleagues in the field even if not the university.