VA staff service/recognition is no different for plat, gold, silver, red or nobody. Every one gets treated the same (IMHO).
That's just not true! I get the "Welcome back" where as my VFF red colleagues don't
I don't think I have ever got so much as a "welcome back" as a Platinum flying with VA.
If you happen to live ridiculously close to an airport or getting to an airport with a VL is positively inexpensive, the ability to use the VL whether flying or not & feel no shame about regularly scarfing $60 worth of VA's food & booze (based on the price VA charges NR's for access) could be useful.
Otherwise HH Diamond is the only real advantage over SG
Platinum doesn't get you anytime lounge access, and in my experience VA lounge staff strictly enforce the boarding pass for the day of travel rule. The only additional lounge benefits with Platinum over Gold are the number of guests allowed (3 vs 1 at Virgin lounges), lounge access on arrival (but this applies to Virgin lounges only, so you can't do it internationally, which is when it would be really useful) and in a few cases the level of lounge you can access when travelling internationally (e.g. Etihad First vs Business lounge in AUH). The EY first lounge is awesome, but clearly that's not much use to you unless you're going to be in AUH, and the Business lounge there isn't exactly a hovel!
I agree that HH Diamond is a great benefit, but also bear in mind that it's a one-off. For me Row 3 access is a decent benefit - I know people say you have a good chance of getting Row 3 anyway, but I suspect that's really only if you're travelling alone. As a Platinum, I get Row 3 virtually every time, even when travelling with my wife and kids. In fact, once the in-laws were travelling with us as well, and I managed to get all 6 Row 3 seats for us! Having said that, I can live with sitting in a different row from time to time if I have to. The upgrades are great if you can use them - especially on longer flights - but a lot of people can't use them as they never fly on flexi tickets. The bonus points and fly ahead benefits were good, but both of those have recently been removed if you're travelling on the cheapest fares.
Overall, I wouldn't bother going out of my way to reach Velocity Platinum unless you are willing/able to fly on Elevate or Freedom fares so you can maximise the benefits. If you mostly fly on the cheapest domestic fares, then I really don't think you'll notice much difference between Gold and Platinum. I've already decided not to bother going out of my way to retain Platinum status, even though I only need another 200 SCs by August to do so.