I think a lot of us get started with 401k’s
that are offered by our companies, and I don’t think Share Builder is a big player in that market. I’ve had 401k’s (and a 403B and a 401a) from Fidelity, Wells Fargo, and now Schwab, plus a TIAA/CREF and there was another one I’ve forgotten about . When I’ve switched jobs I’ve rolled any 401k stuff into Fidelity just to keep it all in one place (except for the TIAA/CREF, which is a different sort of beast).
Fidelity has really good customer service, and that’s worth something when you are having a 40-year relationship with a company . They’re a big local company, too, big employer in my field, so that gives me some warm fuzzies. I admit I haven’t done the research to know if they’re the absolute best dollar value around but my accounts have been doing OK relative to the market. (and I’m sure they know that happy customers are probably not going to do all the work to switch)