Even people who rode both aluminium and carbon wheels will have different opinion on that question or on the pros and cons of carbon-aluminium. I read lot of stories of carbon failure that brought some riders back to aluminium rims. Also stories of riders who were destroying aluminium rims all the time, then made the switch to carbon and they will swear that carbon is more resistant. I think that just show that all carbon rims and all aluminium rims are not that created equals and also it may depend on riding style/area as mentioned by drdre above. A good aluminium wheel will generally be more supple and if it dents, you can often fix it. While carbon will generally be lighter (but some AM/enduro wheels will be close to a good aluminium one) it also more stiff/direct.Question while I narrow my search - for a complete build would the extra 1K for the carbon wheels be worth it?
Here's my personal experience. When I bought my Ripmo, I got some We Are One wheels (Insider rim 27mm, dtswiss 350, sapim cx-ray spokes), around 1700g. These rim are known to be relatively supple for carbon. Rode one season with DHF 2.5/Aggressor 2.5, then Dissector 2.4/Rekon 2.4. At the end of last season, I bought some beefier tire (Magic Mary 2.6/Big Betty 2.4) and installed them on my stock Ibis wheelset which is aluminum 35mm inner width. The difference between the two setup is really amazing, almost like two different bikes. It's due to a mix of more damp tire carcass, weight (probably 2 pounds more for the aluminium setup with beefier tires), larger inner width rims and possibly material of rim. On gnarly trails (rocky, with ledge, roots, steep rock slabs, etc) I preferred the aluminium setup. The bike feels like a monster truck, is more compose and also stable while in the air. The carbon setup with lighter tires is definitely faster, easier to throw around, easier when you have punchy moves or small steep climb. It's really easier to pump the bike and it feel more dynamic under you. Full speed into a rock garden it transfers more shatter. Which % of those differences is due to carbon vs aluminium is hard to tell... I would have to try two wheelset with same inner width and tire to be really sure...
So I've decided to keep my Ripmo for really gnarly ride on more enduro style trails while I'm building my Nimble 9 to be more all- around. So I'll use my carbon wheelset with Dissector/Rekon and can alway get 2.6s if I want more cush. I would be curious tp try the N9 in 27.5/2.8 as I find this setup really fun on my son's Middlechild. So is it worth 1000$? I guess it depend on budget, where and how your riding and what you're looking for...