As a VI clone, understandably, there don't appear to be many functional differences between elvis and vim. According to Learning the vi Editor, 6th Edition, the only difference in is that elvis doesn't have incremental searching.
There's unlikely to be much of a learning curve moving from elvis to vim - they are after all both based on vi and at the very least share the same basic commands such as navigation, modes, search.
Most likely if you were to install vim and treat it as your primary editor for a day - you'd already know which features (if any) elvis offers that you'd miss, and any inconveniences vim might give you (if any).
I'm not that familiar with elvis, but some of the advantages of vim are the abundance of plugins, and that it's maintained. The latest version of vim (7.3) was released in 2010, the latest version of elvis (2.2.0) was released in 2003.
Note: as commented by alexios - changing distro doesn't mean you can't simply continue to use elvis.