Is that difference that substantial?
price wise it is - but, I mean, how noticeable is the grinding performances are?

Uh, how are you using it? We cant really tell you anything other than qualitative build differences without an idea of how it gets used.

+1.
Actually, more for comparison, both in price and espresso grinding quality would be Rocky versus Preciso.
Though I owned a Rocky 7-8 years ago, I can say with a fair amount of certainty the quality of espresso grind from both will be quite good. The Preciso allows a bit more micro adjusting. Also, the Preciso is designed to do everything from espresso to French press with, adjusting back and forth quickly and effortlessly.
Not quite so with the Rocky, which is mainly an espresso grinder.
Little to no waste with the Preciso, a bit more messy with the Rocky.
The Rocky is mostly metal, and feels substantial. The Preciso has a hard plastic body. This has not proven to be a detriment in my usage pattern.
One thing to know is the Preciso is fitted with conical burrs.

mostly espresso!

For what you'd pay for the Rocky, you should be able to find a refurbished Vario on Baratza's website. They go in and out of stock, but I'd say the wait is well worth it. For someone who is primarily doing espressi, the Vario will give much better results in the cup than either the Virtuoso or the Rocky, and it has some additional features that are nice from a user-friendliness perspective, like programmable dosing. And if you go with one of those two, I think you'll probably end up wishing you had finer settings for grind adjustment, which is another strength of the Vario.

If you want to stay under $300, I'd get a refurbished Preciso or a Pharos.

Having used both, I can say the Rocky would be better for purely espresso purposes, and also has a more rugged build quality, its more of a semi-commercial grinder. The virtuoso on the other hand would be better for press or pour over. The virtuoso doesn't really have enough adjust-ability to recommend it for espresso. As others mentioned, the preciso would be a better choice for all around use, its the same burrs as the virtuoso but with finer settings.

And I'll also second [creative nickname]'s shoutout to the Pharos. If you can handle the manual labor (its a hand grinder, and takes a bit of shaking and whacking to get the grinds out), the Pharos is without a doubt the best espresso grind you can get for the money.

Nate42 wrote: As others mentioned, the preciso would be a better choice for all around use, its the same burrs as the virtuoso but with finer settings.

This is actually incorrect. However, there IS a Preciso you can purchase that Baratza has fitted with Preciso burrs.

Nate42 wrote:Having used both, I can say the Rocky would be better for purely espresso purposes, and also has a more rugged build quality, its more of a semi-commercial grinder.

I owned the doserless Rocky and I don't miss it.

Its adjustments are stepped, so it only has 2 or 3 useful espresso settings; too often the pour required a setting that was between two adjacent notches. Another significant shortcoming is its clumping. My routine required a lot of slapping on the side of the grinder and a lot of finessing with the WDT. The thread Why is the Rancilio Rocky so unpopular here? elaborates on this point and others. Given its premium price, there are better options, notably from Baratza.

For those who already own one, note that there are a number of modifications that improve Rocky's usability listed in this forum's FAQs and Favorites (search for "Rocky").

I agree completely, the Rocky I used belonged to a friend of mine, and I didn't particularly enjoy using it. I'm not recommending it per se, I just think that it would be probably a better choice for espresso only than virtuoso. Between Rocky and Virtuoso, the "right" answer is probably neither.

IMAWriter wrote:This is actually incorrect. However, there IS a Preciso you can purchase that Baratza has fitted with Preciso burrs.

I had it in my head that newer virtuosos were shipping with Preciso burrs by default. I apologize if I'm spreading misinformation.