Due to the road and off road conditions near me I’ve always used Slime inner tubes. At least twice a year the farmers cut their hedgerows creating a lot of small, sharp bits of wood.
I’m getting a gravel bike soon and that will be “tubeless ready” and I’m not sure whether to give that a go or stick with my tried and tested solution.
Any thoughts or opinions gratefully received. 
Go proper tubeless, it’s much lighter, the tyres feel better (more grip), and it also helps preventing pinch flats, not only thorn pricks.
(…but then I tried using the slime tubes on my commuter bike, and they wouldn’t seal at all. You seem to have more luck with them)
Yeah, they’ve always worked well for me. Which is why I’m not sure about doing something different.
Try fixing a slime tube that’s punctured
By ‘fix’, are you talking about patching the tube for future use, or something like replacing it with a spare tube in the wheel when out on a ride?
My point was that fixing a slime tube is a non starter, where as tubeless you can use the rubber plug / dart solutions
OK, got it.
British understatement when it comes to the problem at hand.
Slime tubes are heavy and low performance which is why you never see them discussed on forums like this. They probably have high rolling resistance as well.
If one doesn’t care then couple them with tractor tires and you’ll probably never get a flat. They worked great on my kids 24" mountain bike!
Tubeless, just keep up with make sure to top off the sealant periodically.
When I replace my MTB tyres I usually find 3 - 5 thorns in them so I know the Slime works for me. Will the tubeless sealant work as well? Is the sealant lighter than Slime? What’s the performance difference?
I think I should have listed these questions at the beginning but your response has helped shape my thoughts.
Sealant should work perfectly on thorns. I rode in an area with goat heads. I’d get 20 of them stuck to my tires on each ride. They would all seal.
Slime tubes weigh like 400 grams plus you are probably losing 20+ watts in rolling resistance. People train for months to get 20 extra watts. 
Tubeless, on the other hand, can be high maintenance. You need to learn the ins and outs and how to plug one out on a trail.
Thanks.