Hmm. I do not follow those two stocks anymore but my remisier does follow Sino Grand. I hold no stake in them either.
From my recollection though,
Rex Int'l is a highly volatile and speculative stock. Its value will really require a lot patience given the current poor outlook for oil and its lack of earnings. Krisenergy may be a good comparison of a company with track record and strong backers. That being said, if you understand their technology well (I don't get how it works) - it could be quite groundbreaking if applied to other areas like shale oil and such. But it still requires a better oil price for fruitful returns. Rex does have Fidelity on board so that may be interesting.
Sino Grandness may have the issue of the S-chip stigma. Though seemingly better run with astute investors like Asdew Acquisitions and the Thai investor on board - one cannot be too careful with this chinese companies not based in Singapore. That being said - what is comfortable is rarely profitable. IF you can dig into the numbers and justify the existence and growth of the company - I would think Sino Grandness may make a better buy then Rex given its an everyday product (loquat juice) that may actually be quite marketable overseas - scale and growth..