It's not just the content in terms of RDA that you need to look at but the type of vitamins that they are using, primarily if the source is synthetic or not, as it affects the way your body will be able to utilise the content of the tablet. For example vitamin d is available as d2 & d3, d2 is often synthetic & is very poorly absorbed. It's commonly used though because it is much cheaper to produce. Similarly with vitamin e, dl-alpha is synthetic d-alpha is not.
Most vitamins are absorbed in the small intestine, so having tablets that are coated with a time release coating is beneficial as the nutrients will survive the acidity of the stomach better & as your body can only absorb so much of each nutrient at a time, the coating means you will be able to absorb much more than the same tablet uncoated, which is particularly important with water soluble b vitamins (especially so for what I've read about bypass patients with absorption issues / hair loss problems)
It's also wise to avoid any product that contains an 'E' number or a product where the 1st ingredient is a bulking agent as both are signs of a cheap ineffective product, many big brands do this too! So a cheaper product doesn't always mean it's a bad product.
There is a standard in the vitamin industry called GMP (good manufacturing practise) which guarantees that what is written on the label is in the product, as products are independently tested. Similarly, pots labelled pharmaceutical grade & bio-available are worth looking out for as you will be getting a better product.
I hope my limited knowledge helps someone!