Yep, I had two, but I was breaking a chain and completed on first house at least a month before completing on the new house so less of an issue in instantly transferring money.
But no reason why you can’t do this, it will cost more probably. And it could be a pro or con – the con being another bunch of idiots to deal with, the pro being they are both being paid to act in your interests so if one starts stalling you instruct the other guys to start kicking them.
If you switch to a single one, they you are likely to pay out any costs they have on your behalf, but they can also pass any searches to the new solicitors.
You can have as many solicitors representing you as you like