Between the Hardrock and the Hoss, the Hoss is a much better spec'ed bike, I don’t think that there is much to choose between the Trailhead and Hoss, whichever fits better.
Even the top of the line Hardrock has mechanical discs, mixed Alivio/Acera components, Suntour fork, etc. These are recreational level components. The Hoss has a Deore/XT mix, hydraulic brakes, a 20mm thru axle Dirt Jumper 2 fork, etc., it is not a badly spec'ed bike. It is a bit gimmicky that they call it a Clydesdale bike as you will find the same level of components on a Norco Ari or a Giant Arete, which are both women’s specific bikes.
You may want to look at some of the Norco bikes as well, a Sasquatch or Bigfoot would be reasonable choices. Giant, Fisher, Cannondale, Trek, etc. all make similar bikes but I am partial to Norco.
You need to give some thought to what sort of riding you will actually do before heading off to the store with your wheelbarrow full of cash. I bought a mountain bike thinking I would ride mostly cross country but have ended up doing way more downhill and trails with man made obstacles, I wish I had picked a frame with a slacker head angle.
What breaks? Assuming you are riding harder trails:
- rear derailleur, these hit things when your rear wheel slides off an obstacle. Most frames have a breakaway derailleur hanger that is meant to sacrifice itself to preserve the derailleur but the derailleur cage often gets bent. You can usually straighten them out and more expensive does not necessarily mean less bent.
- wheels come out of true or flat spot. The harder you go the more you need a serious rim, ride what the bike comes with and then look into something like a Sun Double Track if the rims give you too much trouble.
- plastic covers/gear indicators on shifters, send your bike for an unmanned flight and you are pretty much sure to break the gear indicators off, this is purely cosmetic.
- chain slap/chain coming off, this is not really something breaking but when you get bouncing down a trail the derailleur is going to bounce like mad and the chain will hit/gouge the chainstay and you will sooner or later have your chain come right off. You will see a lot of guys running single rings up front with a chain guide to keep this problem at bay. At a minimum, take an old tube and cut it in half and wrap your chainstay (secure it with zip ties) to keep your chain from eating your paint.
- seat rails/seatposts, an unplanned rapid descent onto your saddle will break/bend the seatpost rails or potentially the seat post. The no name posts and saddles that come with most bikes in this price range bend pretty easily.
- axles, if you go with a standard quick release it is pretty common to bend or break an axle.
As for grips, do yourself a favour and get some lock on grips right away. These stay put and also mean you can take the grip off in a flash if necessary.