If I were to consolidate everything at one company, it would be Fidelity, as I prefer their customer interface. Most of my holdings are at Fidelity. I don't have problems with the web site or having to do silly things to make the situation fit the software like I have with Vanguard. I am happy with their offerings and service over multiple accounts. They have cheap index funds (Spartan) as well as a few managed funds I have owned for a long time. They have some excellent commission-free ETF's available as well. Vanguard has experienced a lot of growing pains over the years and they now have a target drawn on their back. I don't think they will go out of business, but I do think the business model will change.
When I started out investing in mutual funds, everything was done by check and US Mail. You could not hold one company's funds at another company. If you wanted to own individual stocks, you signed on with a broker or found a way to get into a DRP plan. As a result, I have legacy accounts at a couple of mutual fund companies. Some of those accounts are decades old and have done very well. I probably should move the shares to Fidelity, but transaction costs would increase. Same thing with the old DRP accounts. Some of those are also decades old.
I have a retirement account at Vanguard, as well as a taxable account. The retirement account is a rollover and is invested in Wellington. Same issue with transaction costs, not cost effective to move. The taxable account is invested in $0 commission Vanguard ETF's. I also have a taxable account with Schwab, as they offer some ETF's I like and offer $0 commission trades on those.
Although this set-up is unnecessarily complicated, I find it to be easy to track through Personal Capital. In fact, the account aggregation software has de-motivated me from consolidating. My guess is you have no reason NOT to consolidate, as you likely started investing in a more modern, internet-based environment. However, if you have old accounts floating around, look at the consequences of consolidating before you decide to do so.