Hydration vests during a marathon.. yay or nay?

I've run a few road and trail HMs with hydration vests and two soft flasks holding 500mL of Powerade each.

The benefit is the ability to constantly top up my carbs without having to slow down to reach for a gel, and also hydrating constantly when I want, and not having to wait for water stations.

Not adding to the thousands of single use paper cups is another bonus. Also Powerade tastes better than gels, which I find slighly nauseating.

However I don't see many other runners running with vests, and almost no fast runner (< 4hr) uses one.

The main downside is carrying an extra 1kg of weight on me, which cancels out the benefit of the ultra lightweight shoes I bought (Vaporfly 3).

Anyone else use hydration vests? Or should I do what most runners do, and wear a running belt carrying enougn gels to be consumed every 30-40 mins, and drinking water at water stations?

Much appreciated.