Taking money from a “new” VC firm has a little risk, but it’s minor.
The real negative is money from a un-respected firm or Partner (GP). Even this is minor, but a clear negative. It just makes raising the next round that much harder.
And if you have a highly respected GP / fund in the round, it makes raising the next round that much easier.
Most “new” VC firms actually have fairly highly respected GPs in them … or they wouldn’t be able to raise a fund. Often, they were successful GPs at prior firms, etc. And firms have 10–12+ year lifetimes, minimum. A new firm isn’t going anywhere.
And in fact, GP/partner turnover at bigger funds much more common these days. So Old Firm GPs actually have less stability than they used to.
Net net: focus more on the GP than the firm here.
Also — all money is green. First, pick who you trust. Second, pick who can help the most. This includes the next round. If a new fund meets these criteria best, pick them. If it’s Sequoia and they’ve given you a term sheet, that’s good too!