Based on US-China tax treaty Article 19, teachers and researchers may have 3 year income tax exemption. I see people get this benefit with J visa, but the treaty didn't say it applies to J visa only.
On the other hand, H1B workers generally have to pay social security and medicare tax. The exclusions of social security tax are under IRC section 3121 (b). The exclusion normally applies to F, J, M and Q visas only.