The pricing is so good that it's the only way I do agentic coding now. I've never spent more than $40 in a month on Opus, and I give it large specs to work on. I usually spend $20 or so.
You do get Opus 4.6, and it's really affordable. I usually go over my limits, but I'm yet to spend more than 5 USD on the surcharges.
Not seen a reason to switch, but YMMV depending on what you're doing and how you work.