If you mean the all in one tanks, they're certainly good quality, but upgradability is a bit limited as things are built a bit specifically. If you wanted a bigger skimmer, or to fit reactors, etc down the line it might be tricky to retrofit things.

If you find one that's exactly what you're after, then go for it, but at least make sure there isn't a similar specification regular set up available for a similar price.

I'd always prefer to buy a cabinet and tank from a tank builder, who'll supply a suitable sump and build the weir, drill the tank, etc, then you can buy all the equipment you want as you go.