The main things to look out for while choose a artificial grass:
Stitches per square meter
The stitches per square meter tell you how dense the artificial grass is - the more stitches per square meter, the more dense and heavy tactile the turf. A basic artificial grass for landscaping has at least 14700 stitches/㎡ and increases from here. An artificial lawn with this number of stitches really is the minimum amount you should be looking at, otherwise your grass will flatten within a matter of days.
The total weight of the artificial grass along side the stitches per square meter also provide an indication as to how good the synthetic turf is. Again, the minimum weight should never be below 1,500 grams per square metre for a permanent fitting. Skyroad Turf produces artificial grass with average weight of 2300 grams per square meter. This weight is the backing and stands combined and indicates the durability to an extent of the artificial lawns. Otherwise you will find the cheaper and lighter grasses tend to shed strands/fibers quickly as the backing is much thinner & the stands aren't as re-enforced.
In general the pile height increases along with the price as you are getting longer stands of grass. The pile height is more of a personal preference to consider along side the previous points mentioned.
Please do not just choose the most expensive or pursue the low price products ranstam when selecting one. It does not mean this is the best grass that will suit your needs. Start by working backwards from your budget, calculating the price per square meter you can go up to. Then look at what pile heights you are open to and narrow down the selections to which are within your budget. With the remaining grasses look at the 'total weight(Dtex)' for each as well as the 'stitches / square meter'.