I don't know much about the original Synthi, but to me the Synthi V sounds great.
I like the added features. There might be some wishes about them like the following feature request i have, even though i don't own the Synthi V now.
I think it could be good, if at least the "Offset" parameters in the Modulations "Parameters" and especially in the "Groups" could be assigned a MIDI CC and also could be automated in a DAW, so they also could act as performance Macros.
One thing i don't agree with Arturia in is, that i still think a metering for the output level especially in standalone mode is important for any application. When creating presets/ working in standalone mode a output meter is essentiel. It does'nt have to be original meters, but just one for the application. It could be the same for all applications and put in the top panel.
Anyway - Synthi V is a fine synth.