There are several benefits associated with switching to spread.
1. A better capability to combo/PA complicated patterns
2. Improved skill at all songs in a short time frame
3. Improved reading of patterns
4. Vastly improved speed
I don't play spread, so you're better of asking somebody who does.
But what I have listed are the basics, but they comprise nearly all facets of spread playing. Most people go from FCing VDs/Challengings with one hand (usually takes a few months) to FC'ing VCs within a few weeks for spread.
However, do not feel pressured to switch. Stay with what fits you best, be that one handed or spread.
~Bynary Fission