I was recently called upon to cite the practical and aesthetic advantages of both the adjustable waist band and common-or-garden belt loops on trousers. Having experienced people struggling with this choice in the past, I feel I can help make things a little clearer if you are faced with the same problem.
Side adjusters on suits are generally considered a style for more traditionally cut trousers and are mostly seen on bespoke suits or with trousers that require brace buttons - the idea being that if you do not wear braces then you can buckle the adjusters.
Belt loops give a more contemporary look to a suit and are much more popular in the rest of the world. Personally, I prefer side adjusters as i think they give a cleaner line.
If it’s the belt loop system you’ve plumped for though, Hackett stocks an extensive range of belts and braces to help you finish the look.