(1) FancyHands, having been around a lot longer, has far better execution and delivery. Email, phone, an app, recording through the app--many ways to give a task assignment. I usually don't want to text them, I forward them emails to take action upon or simply leave a voice message.
(2) Jarvis is unlimited tasks. THAT is a big one for me. If there ever were a service that were at or somewhat approaching FancyHands quality with unlimited tasks, I'd be on it in a heartbeat. For the time being, I've been using Visa Signature Concierge for tasks that don't require a FancyHands level of attention paid to them, since they are unlimited and free if you have a Visa Signature card.