Which is the best for me from the following usual suspects

Mavic 717, Stans 355, DT Swiss 4.2 (I think those are the right ones)

I weigh 65 kgs, they would be going on a trek xc hardtail, to be used for marathon events etc, and will run them tubeless with Stans.

Was leaning toward the 355's because I assume they are tubeless ready ? and wont need those uber expensive rubber stans rim strips but maybe wrong. What ar the pro's and cons of any of the rim choices

Er… if you're planning on running tubeless with Stans, why not go for the Stans? 😕

It's dead easy, just yellow rim tape, sealant and a track pump required on all the tyres I've tried with my Flows.

They don't come with the yellow tape and valves as standard, but they're not expensive.

Stan's 355 IMO,

I used to ride 717 on my hardtail but decided to go Stan's on my new wheels on a ful suss. They have taken as much as the 717s did and are lighter. If you are thinking tubeless then that suggests Stan's even more.

I have heard that the DT rims are soft but that might be rubbish.

Er… if you're planning on running tubeless with Stans, why not go for the Stans?

Yes, I know it did seem like I was asking for that 🙂
I never really had a big problem with running Stans tubeless conversions with the rubber rim strips, its always worked fine for me, so if either the Mavic or the DT wheels were way better in termns of stiffness, durability or weight than the 355's then I would ge that way. If the Stans are the equal or better than the others in most ways then the fact that they are easier to run tubeless then its a "win win" for the 355's

355s are virtually sold out – to be replaced by the crest rim any day now. Slightly lighter and wider internally