Hi there,
From a pure valuation perspective - BABA seems like the better value. It trades at cheaper valuations across all metrics except when looking at price or EV to sales. Outside of that, if you are looking at earnings, cash flows, EBITDA, BABA is the better deal. Furthermore, although BABA and AMZN have similar expected growth rates, BABA comes in slightly higher ( a few percentage points). Finally, BABA is also more profitable with much higher EBIT, EBITA, Net Income and Cash flow margins. In most cases, they are double that of AMZN.
Based purely on fundamentals alone, personally I would select BABA. However, there is the added geopolitical risk to consider with BABA. This has come to light recently as Chinese regulators are looking to make decision that may cause the company to dispose some of its assets. This has pressure the stock in recent months as there exists uncertainty around just how much it will impact the company. It could have a material impact, or it may not but investors don't like uncertainty as it increases the risk profile. A good way to sum up the regulations is that it is not likely to impact the company in the short term (financially) but will open the door to increased competition.
BABA is a company that seems better valued, has comparable growth profile and is more profitable. Whether you think the additional geopolitical risk is warranted will be up to each individual's risk profile.
Mat