My opinion is as Dave kind of said, depends on your block. If they are already real close then there isn't going to be much difference. If they are off a significant amount you may see gains but probably slight.

I've run a big Hughes flat tappet in 2 different blocks with the same lifters and never had a problem, others have.

BTW I've never yet bushed lifters in any of my engines but I haven't built a lot of them like a performance machine shop would, just my own personal engines.