You get what you pay for "RELATIVELY" Most if not all 20V or higher tools will do the job for the average home owner. The batteries and the power management circuitry along with a smart charter is what makes many good tools a higher price.
-Cheap tools come with the cheapest lithium cells that have a short life and short charge cycle along with no on board temp./over power/underpower protection circuitry.
-Cheap tools have terrible chargers, often they are just a dressed up Ac power adaptor that pushes a volt or two above the battery's labeled rating. Besides protection the circuitry charges and monitors individual cells or banks of cells not just one big push of power to charge. Fast chargers are a life killer for lithium batteries, if you can slow charge you'll get a lot more charging cycles. Keeping above 50% and below 80% for long term storage helps with maximum capacity when going for 100% charge.
-Most drills/die grinders ect. have plastic/nylon drive and planetary gears, There are a few exceptions like Dewalt-Milwaukee-Bosh but even those have been fazing out metal inner bits in lower end models.
-All cordless impacts are a steel rotating hammer assembly and most have steel planetary sets.
-Many higher quality cordless tools have a 1year or better warranty
-True power ratings like TQ, Speed, RPMs, and run time ect are all over the place. This is were higher priced companies can afford to test and rate for the buyer.....The batteries are the cause of 90% of the good or bad rating.
Harbor Freight stuff is IMO middle of the road in quality. That does not mean they are crap, their stuff fits 3/4 of what the Average-Joe needs at a stellar price. Their chargers are smart but not monitoring type. The cells they use are on the cheap side. Their warranty is pretty good. If your not going to be using it everyday for a living or running it into the ground on some big one time job under a short schedule they are in my top 5 power tools that are not pricy high end.
Hilti IMO is the best, they run circles around most other power tools, but they are stupid expensive. Best bet is used on eBay or a local pawn shop as they get stolen all the time.