Financial risk is higher with Project B, i.e., more money is at risk. Further, larger projects usually have more tasks, more things to go wrong, than smaller ones. Both projects are attractive, with the key tradeoffs between risk and return. This simply means that more money is better than less, even when discounted. But focusing on this fact misdirects attention from other important considerations.
More realistic scenarios suggest several opportunities.
Execute one now, one later. In addition to having lower risk, Project A generates cash to finance the larger Project B. Execute Project A twice. As the better choice than one B. Executing the same project twice or more should reduce risk since learning from the first execution is applicable to subsequent ones. There are no contradictions between NPV and IRR in these examples. Rather they highlight the need for both.