HA with argon m2 on Rb4 4g or 8g or VM

I’m running HA on RB3+ and I’m planning to buy argon one m2 also I’ve RB4 4gb so is Home assistant OS will run smoothly on RB4 4gb or should I buy RB4 8gb.
Another solution is to buy dell optiplex and run HA on VM. Which solution is better and stable?

Thanks In advance