I have an ARP Solina and ARP Omni 2.
They sound very similar but not identical which surprises me because I think they would have used the same circuitry for the strings.
The Omni has a bit more of an edge to it. The Solina has a more glassy sound, but I prefer it with a phase shifter the way Styx has it in the middle of Come Sail Away.
I always thought that the Solina sound would be an interesting sound in a Mellotron with the tape warble affecting it.
I think I paid $800.00 for the Solina back in 2005 and $300.00 for the Omni in 1993.
In the 70's I think the Solina came out before the Omni, but I could be wrong.