Given the O.P.'s hypothetical numbers, it seems like a no-brainer to me.
Since they cost the same, Buy the ELR. If you like it, you are done. If you don't like it, you can probably sell it for more than your cost (effectively pocketing the incentives).
You can always buy a Volt later, they are relatively common and still being made unlike the ELR.
Nothing about the Volt price screams "deal of the century". How many chances will you have to buy a new ELR at that price?
Since they cost the same, Buy the ELR. If you like it, you are done. If you don't like it, you can probably sell it for more than your cost (effectively pocketing the incentives).
You can always buy a Volt later, they are relatively common and still being made unlike the ELR.
Nothing about the Volt price screams "deal of the century". How many chances will you have to buy a new ELR at that price?