Another likely difference: expectations for additional fundraising. Paul Graham has advocated for startups to be "default alive" and YC has stated that they are neutral on whether startups choose to do additional fundraising rounds. In contrast, since a16z is a VC firm that is coming down market (and based on their track record), it seems very likely that they will encourage companies to delay profitability in favor of growth and to raise additional rounds (that a16z will participate in).