Not really, gain in the digital world has less analog artifacts (almost 0). When you put gain in in the analog world, you are bringing with it added sound. In the digital world, if it didn't get recorded it doesn't boost (for all practical purposes). But if you clip at the source, you can't fix that. Analog clipping sometimes sound good, digital clipping (which is what the sound is once in the computer) sounds like shite and it can't be fixed.
Digital clip is why I suggested tracking at a lower volume to make sure you don't clip at the source. Also, some of the hiss you may be hearing could be in the amplifier going to the speakers. Get a good track, good performance, don't clip and then in the MP3 clinic we can help you dial it in.
I assume you are going to play the guitar and then come back with the vocals? If so, you will get the balance right during mixing stage.