As a high school student, I was unable to get into any of my local college's classes before they filled up, so I decided to gain some professional experience through a job or internship. I applied to a few places, one of which I started to make progress with. I got a response and was sent an online test for basic skills (programming / web development), then a written assessment of some things, then an interview, then another interview, and now I'm waiting to hear back from them after my background check is done and references contacted. This has all happened quite slowly and has taken about a month now. I decided about a week ago that, although things were looking good with this company, it would be wasted time not to apply for other things while waiting for various things. I'll call this company A.
So, I contacted another company, and things went faster with them. An interview was scheduled, I filled out an application, and then today I did a followup interview and did my first day on the internship. I'll call this company B.
The problem is that I would prefer to work with Company A. With company A, I would be working on a team/teams whom I would be able to ask questions, get help from, etc. and would be working on code and websites that are already built. As someone with not much experience, this would be better for me and the company. Company B is a law firm and I'm working on creating a website from scratch there. While I have made basic websites before as a hobby, I wouldn't be able to handle scaling, database structuring, code structuring, load handling, caching, etc., as well as someone with more experience in the field.
My dilemma here is this: I know I shouldn't mention the other job until I actually have it - I may change my mind or not get accepted to it, in which case I've made it known that this was my plan B and that my being there wasn't my best option - but in the event that I do, maybe after two or three days interning, get accepted to the other company, I wouldn't want to out-of-the-blue just leave.
The way I handled this is hardly ideal. After a few hours of situating myself and getting started on the design, I went in and told the guy I interviewed with that I had applied at another place prior to applying there, and that, due to the other being a paid internship, would likely accept the position there than stay. I had mentioned in the interview, when asked about my pay, that I was there for experience as my top concern, and was thus under the impression that the internship I had started there was unpaid. Granted, even then, it was an incredibly rude thing for me to say, but as soon as I brought it up, I realized how rude just the idea of telling one employer you would rather work somewhere else is, and started fumbling around for a good explanation. I also explained that he would probably want and need someone with more experience for what he was asking and my preference of Company A was also largely because of my belief that I was unfit for what he was asking. He told me not to worry about that, that he wasn't being deceived at all, he knew where I stood in terms of experience and that I should give it my best and we would see how things turn out after a week. All said and done, I was told that the internship there IS paid and that he understood my position (he was really nice and I feel quite embarrassed about the whole thing).
What should I have done? Should I have waited to hear back from the first company and then leave abruptly? I personally see this as quite rude, though I understand the logic in not counting my eggs before they hatch. Then again, I imagine it might be more rude to tell someone that, even though I don't have the position for sure, I would rather work somewhere else if given the chance.
I'm young and naive, so I would love some wisdom of the experienced.