...I know a lot of people do this with plugins while tracking...
Then...you know a lot of idiots and shouldn't listen to them. And quit trying to take short cuts. Would you even think about having two guitarist playing through the same amp at one time? This is the type of thing someone who is JUST STARTING recording may think of doing to save time. If anyone tells you to do this, or that it works just fine...they have no idea of what they're talking about and should be ignored...or given a 3 Stooges style slap in the face and poke in the eye.
It's ok to do that if the plugin offers a stereo option and you hard pan the input DI's.I know a lot of people do this with plugins...
Marshall? JPM for example has four inputs.
Obviously the original question implies that the DIs are tightly played double takes - not different phrases - which will be different.
I know a lot of people do this with plugins while tracking, but it would be interesting to know if anyone reamped it like that with good results.