Before I start... everyone has their own opinions. So take this with a salt-lick grain of salt.

If it were my money and I was starting over again, I would go with the Intellijel Atlantis. It's based on the Roland MS101. It's a complete synth in Eurorack.

The other option is a Behringer Neutron. It's less expensive and doesn't require being mounted in Eurorack and comes with USB and DIN MIDI.

If you outgrow either the Atlantis or the Neutron, the resell value on them is decent.