In reply to Laurence20: This is a slightly controversial one, that definitely splits opinion.
I have used 60cm x 8mm draws, captive both ends for 13+ years. Although I also carry several 'free' 60cm slings and plenty of spare wiregates.
There are several clear and significant advantages.
1 - once deployed they are quicker and easier to rack whilst still extended. Just clip one krab to the other. This makes life considerably easier for the second once they are aware of it.
2 - they are significantly easier to re-rack (i.e. triple up again). This is especially true in Winter when wearing gloves.
On the other hand there are several disadvantages:
1 - There is a 'nack' to extending them. One krab needs to go back through the other or you end up with the sling knotted around one of the krabs. (Not a safety issue, just a faff to sort out.)
2 - You can't easily rack them over your shoulder as you can if the krabs are loose.
3 - There is a potential
complete failure mechanism as mentioned by other posters. This is actually very unlikely to occur IF you are familiar with such draws and is easily spotted but you can't get away from it.
For me, the fact they are still easy enough to rack and use whilst fully extended beats the other considerations.