Not looking to go off on some drawn out tangent discussion....
.....but sometimes, one DI may just sound better than another. They all do the same thing AFA converting your guitar singal...but the DI circuits are not all 100% identical, so you might find a standalone DI that could sound better *to you* than your interface DI....but it may not be a dramatic difference if that's what you are expecting AFA making your guitar sound better.
Hate to say it....it could be your sim, it could be the guitar, maybe your tonal selections, and/or a little of the DI quality...or it could be a combination of all...so you have to keep dialing it in until you get what you want, and that might require that you make some changes to any or all of the above.
Hell....maybe even try going with an amp and mic!