I currently have the standard 3×9 setup on my spesh xc full susser . i quite fancy a single ring up front ,so my question is should i keep the 9 speed cassette i’ve already got or go for a 10 speed ? What are the pros and cons of both and what size chainring up front would you recommend for each setup . I like uphill climbs and love giving it the beans downhill so a happy medium would be great if that’s possible . thanks all .

1×10 with an 11-36T cassette gives you a slightly wider gear range.

Other than that, not very much point.

BUT… The wider gear range is worthwhile IMO.

36 as opposed to 34 is a marginal advantage of course but 10sp allows a clutch mech which means simpler chain retention with top guide only unless downhilling. For me that makes it worth going 10 spd.

If you can go uphill easily on a 32/32 then stick with what you’ve got (or mebbe stretch to an 11-34 cassette at the back)

I can’t so I’ve gone 1×10 (plus I wanted a clutch mech)

How about 1×10 with the General Lee conversion? Especially useful if you will be doing xc/allround cycling. I’m looking into this option personally.

General lee conversion?

For me 32 and 11-36 is a good compromise
Low enough gear to get up without busting my knees
And not get left behind on the road / flat smooth bits

But everyone is different you many need to try a few rings to see what suits you
There is no right or wrong

General lee is a kit to convert an Sram 10 speed cassette to an 11-40 cassette giving a wider range. I have one with a Absolute black 30 tooth chainring to go 1×10 when the new bike is built up. More info see this thread and MrTee’s Norco on page 3
http://singletrackworld.com/forum/topic/wolf-tooth-components-xx1-type-chainring/page/3

1×10 will give you the opportunity to run a clutch mech, which really is worth it in my opinion. Running a 35-tooth front ring, never had issues keeping up wither others (even those running triple) on my Meta 5. Even fine on long days, did a ~70k ride today without any issues.

Pridds I hope you are riding a 29er

Nope its an old school 26er (carbon Nomad) but i live in the Lakes and am happy to compromise to get lower gearing

1×10, because: Bigger range (11-36), Clutch mech.

I run 32 and can get up pretty much everything I want. YMMV depending on fitness / technique / where you ride.

1×10 makes more sense if you have the cash to make the change. 1×9 canbe hard(er) work to add to Superficial’s advice Cadence – we all spin at different speeds, the slower you legs go (confortably) the bigger the front chain ring to get the same speed and the harder the lower gear will be. I really struggled with a 32 but a 36 worked fine (when I was a lot fitter) I now run 2×9 22/36 for best of both.
Do it in stages drop the big ring and see how you go, that should tell you if you need to up the front. If thats OK drop the granny and just run 1×9 with what you have if you want more upgrade the rest. The chainguide (if you want one) will be the same.

When you go permanent get a proper 1x unramped ring.