I don't have any experience with the HF model, but it is my understanding that the reduction gear is plastic. That simply can't be good for long-term durability.
Also, there is no tool post that makes today's water wheel "systems" so precise and versatile.
FWIW, about $25-$35 more will get you a Grizzly T10097, which is a more specialized setup for sharpening purposes.
I have both the Tormek T-7 and the Grizzly T10010 (10" wheels). The Grizzly was purchased initially due to budget. Later I purchased the Tormek.
Tormek is the ultimate for this type of sharpening, but very pricey. But the secret to getting the most out of these systems is in the jigs, and the very high quality jigs made by Tormek will fit the Grizzly models.
Out-of the box differences:
The T-7 is much better quality. The wheel seemed to be considerably higher quality, and was ready to run, whereas the Grizzly wheel needed truing/dressing. The Tormek motor seemed more powerful. The honing wheel on the Tormek was better, too.
And, of course, the Tormek has the micro-adjust on the tool post.
In addition, the Tormek has a diameter indicator for quick setting of the angle gage, whereas the Wheel on the Grizzly needs to be measured with calipers.
With that said, the Grizzly models, though lacking in refinement, are a great buy. My largest complaint is that it lacks the micro-adjust, but that simply means I have to spend a little extra time setting the angle.
But as far as durability is concerned, I have had no problems whatsoever with the Grizzly. And that is probably the largest concern for all of us plunking down our hard-earned cash.
Looking at the HF model, I realize budget may be a concern (when is it not?).
But I truly believe you will be better served spending just a little extra and at least stepping up to the Grizzly T10097. That way you will at least be set up to use the different jigs later as budget allows.
Consider this:
1.The HF retails for $65. For that money, you get a combination 6" bench grinder/ 8" water wheel. As mentioned above, the gear slowing the water wheel is probably not going to last under hard use. Also remember that you're on your own in devising a method to obtain precise angles on various tools. The probable end-case scenario is that you spent $65 on a 6" bench grinder. If you need a 6" grinder, HF sells one for $45.
2. The Grizzly T10097 retails for $90. It is strictly a water wheel; no fast grinding. But, with the proper jigs, it allows you to sharpen tools that most people either spend a lot of time doing by hand, or paying a shop to do it.
My suggestion for the budget-minded would be the Grizzly machine paired up with Tormek jigs. (Remember, as mentioned above, the jigs are the key to precision with these systems. And the Grizzly jigs leave a lot to be desired.) You don't have to purchase all the jigs at once, just what you need.
If you have an extra C-note, go for the Grizzly T10010. This gives you a 10" wheel (vs. 8") with a stronger motor. Again, paired up with Tormek jigs.
Or if maximum quality, durability, and versatility is the name of the game, Tormek T-3/T-7.
As already mentioned by HELLGAP, the water wheels are not always the answer.
But if you do go that route, my belief is that the extra $25 is an excellent investment.
Good Luck,
Rob