I have a DigiTech RP-150 that I use for recording on to my PC and for practicing. It gets lots of good sounds, lots of cool sounds, and has plenty of effects. It's great for what I use it for.
I took a song to use for my father/daughter dance at my oldest daughter's wedding and edited it. Then I used the RP-150 to add some tremolo guitar to it, which it sorely needed, and then I saved it as a file to play for the dance. It worked great.
As an experiment, I tried three different things through my tube amp live.
- Tele -> RP-150 - best tremolo sound -> 12W/12" tube amp.
- Tele -> tremolo pedal (3 transistors) -> 12W/12" tube amp.
- Tele -> 12W/12" tube amp - built-in tube tremolo.
The RP-150 tremolo came in last place for sound and realism. The three transistor tremolo pedal sounds pretty nice. But nothing, nothing at all, beats the real tube tremolo. With just one guitar and one amp, there's no comparison.
By the time a radio or computer song gets to your ears, it's been processed and compressed ad nauseum, so you may not be able to tell the difference. At a honky-tonk or bar or coffeehouse or church you may or may not be able to tell the difference, depending upon other things. Chances are, only guitar players or amp afficianados will know or care.
But I'll know... and I'll care.
Digital music technology has it's place, and I use it every day, but it is not the same as a real good tube amp. I wouldn't use it on stage at a small church of coffeehouse or bar. I could tell the difference, even if no one else did.