Virtual Assistants -- Service vs. Freelance

Hi all! I run a small marketing agency (by small, I mean tiny, we only have three full-time employees). We do a lot of strategic SEO work and really embed with our client teams to help them build holistic content/search/AI-optimization strategies.

Anyway, I've been working with a virtual assistant I found through a reference, and she was absolutely fantastic, but she's moving on to a full-time role. She was managing our calendars, updating templated audit presentations, and handling a lot of our CRM processes.

I need to hire someone to replace her part-time. I'm not sure how to proceed, so I thought I'd ask here.

I need to decide if I should hire someone contract or it might be be better to hire a managed VA service.

My concerns are:

1. Having to retrain a VA whenever they leave

2. Confidentiality/security concerns

3. Continuity of support

I've been looking at services like Prialto and Belay and the managed element is compelling, but I know a contractor is cheaper. People who've tried both or either, what did you prefer?