I can’t speak as much about Vivid as I can for Stubhub, but I’ll say that SH is VERY buyer friendly. Once you’ve bought tickets, if there is anything at all that goes wrong which is rare, they bend over backwards to make it right. Worst case, they give a full refund but in most cases, they’ll send you comparable or even better seats if there is any issue at all with the ones you bought.
Of course, the downside is that you typically pay out the *** for tickets after all the fees, but the tickets themselves are solidly backed by SH