We are paying ds's rent and he will have the maintenance loan to live on
The problem with doing it that way, is that once the loan hits their account at start of term, they have a full terms-worth of money in their account. If they are stupid (and some are when first going away) they may have blown it all in the first month!
By doing it your way Op, with you drip feeding him a monthly amount for living costs, he cant blow it all at once!
My DS is heading into final year after 2 yrs at uni and a YII year out. He gets min'm loan which we top up for accommodation, then give him a monthly amount for living costs from mid-Sept to end of May. We never considered doing it the other way when he first went, despite him being very sensible.
I do look at what he gets in total compared to full loan, but given that his accommodation costs have varied each year (cheap'ish Northern city, expensive halls, 2nd yr house much cheaper, 4th year house more expensive than 2nd Yr) - I don't really take much notice.
We gave him £300 first year, increased to £350 second (despite him saying he didn't need an increase!) and keeping it same this year (despite him expecting another raise!). He did work through 6th form and at end of first year, and has savings from YII job, but we can afford what we give him easily so prefer him to keep his savings.
Colleagues DD is going - my advice is to start low and then increase if necessary - easier than the other way around! You may find he can't get a job, or like my DS job at end of first year, he couldn't have carried it on into second year due to full STEM timetable.
Fortunately we are relatively close to uni, so travel costs home aren't extortionate and his uni funds all his books.