In live performing if you need to switch between algorithms in less than a second you should consider using two H9 with “next” algo preloaded.
This is needed whatever effect unit you use, it’s not H9 related, including lots of powerful racks (I can’t say about Eventides because I don’t own those 
).
Units that can switch seamlessly between complex algos, eventually managing trails, are essentially dual fx engines in a box…
