There is no substitute for a good guitar amp
I have two: First, a Peavey Classic Series Duel 212 , which is 90 pounds of 120 watt all tube dB monster that sounds wonderful as my main giggin' amp. Second, a Vox Pathfinder 15, which is an astoundingly articulate little solid state jobbie that delivers a nice "vintage" vibe for jam sessions and small gigs.
The most natural sustain, depth, and responsiveness come from a miked amp. Amp modeling technology just isn't there yet for me. I like clean jazz and blues sounds, mildly distorted sounds for classic rock, and those seem to be tough for modeling to do well. It is getting better all the time though....it's like when sampled pianos first came on the market, everyone went crazy for them but in reality it took about 15 years for them to get good. I ended up selling my simulators and I am very happy using mics but I am keeping an open mind and I will try all the new modelers just to see if they have anything to offer me.
What's your budget ? What style of music ? Is it just for home recording ?
For the best sound, an amp is the way to go. However, for convenience, amp modelers like the POD, Behringer V-amp, Yamaha DG Stomp, or the Johnson J Station may be more to your liking. They all do a good job for recording, there's no micing up to deal with, or neighbors calling the police because you are wailing away in the middle of the night.