Shelter 501Mk2 or ZYX R100-02H

On an Avid the ZYX will be too live and revealing for Rock. I would go for Shelter.

I contacted the seller of the cartridges... 2juki from eBay...
He answer me that ZYX R100-02 with a low output is better than Shelter 501Mk2.
His response word for word: "ZYX R100-02L will be better, you can get more sweet and warm sound from song and detail from music".

Yes, but more info even from an interested party is still a useful data point. The mistake is to not take into account just that party's opinion.

Not sure if Pani has heard the specific cart in question that you are asking about, but from reading XYX reviews it seems that they differ across the range with regard to the how live and revealing ia specific cart model is. For example, see dougdeacon's review of the 4D, where he compares it to the UNIverse and concluded that the 4D is a better rock cart.

I see the following advantages in cartridges:
1) the abundance of solid bass, drive and perseverance in LF;
2) high degree of detail and comfort of a mid-range;
3) a fascinating silkiness of HF;
Sorry for my bad English...

I have heard the ZYX R100 on Avid Diva and Acutus. I used to own a ZYX RS30-02 low output version and played it on my Verdier extensively on a variety of tonearms. The ZYX are a champ at bass and PRAT but it lacks a certain warmth and sweetness in mids and highs which is so very much required to enjoy rock. The ZYX is a reference to me for classical music and well recorded Jazz. The 4D is best of the lot for rock, I agree but that is expensive. I had a Denon 103pro prior to ZYX and I enjoyed Dire Straits more on the Denon than on the ZYX, just to give you an idea. The Shelter falls more in line with Denon. In fact it is supposed to be a default upgrade for Denon users/lovers. Hope that helps.