I don't disagree with this. They are indeed a form of equity.

My issue relates to how they're treated with respect to taxation by the various revenue authorities. In the UK, the tax paid on RSU's vesting is related to the personal income tax bracket the individual falls into. Which means for anyone in the UK's higher tax bracket, you end up losing ~50% of the amount vesting as tax.

If these behaved like other forms of equity, ordinary shares, preference shares for instance, they'd be taxed as capital, the gains of which would be taxed 'when you sell them' and at a much lower rate of tax - ~50% lower for a UK higher rate tax payer.

I'd rather a company just pay me a higher basic salary than award RSU's. At least then it's both pensionable and often used as a multiplier at bonus/salary raise calculation time.

Yeah I'm wrong, I was thinking of ESPP, not RSUs.

One benefit is that stock is typically awarded in the form of a multi-year grant, where the number of shares is priced at the time the grant starts. So if the original grant says you get $X worth of stock per year for the next 4 years, and then the stock price goes up 40% in Year 1, you’re now effectively getting $1.4X worth of stock per year for the remaining 3 years.

The taxes on equity are substantially lower than on salary. Also equity compensation can be an order of magnitude higher than any market-based salary would ever be.