From what I understand, it sounds as if the bamboo proceess is worse. Here's my opinion on what is "most" to what is "least" environmentally friendly:

Don't buy more. Mend, patch, or dye what you already have and keep using it.

If you must get more, get it "used"...go to second-hand stores, or join "freecycle" for your area on yahoo groups where you can post what you want for your area and people will give it to you for free if they have it. Also, find friends you can "trade" clothes, etc. with. There are lots of things in good condition that you can find used, and if you can't find it at brick-and-mortar places, try ebay.

THEN if you must buy something new...organic cotton, best would be from a local small business...but if a large retailer, hopefully one that's high on the social/environmental responsibility rating...and hopefully, especially if linens, they'll last you a long time, and you can turn your really old, worn things int rags instead of buying Swiffer disposable cleaning products!!

Worst--buying brand new things you don't really need from a retailer that doesn't really care on a (too) regular basis due to affluenza!!

I agree with all of your points. If you have to purchase a new piece of clothing, check out Patagonia, and review their current project; Footprint Chronicals. They are giving information to the public and looking inward to review how many resources are wasted on, say "one" tee shirt or a fleece made of recycled bottles. I love the fact that they are looking inwardly and sharing and making changes. Truly concerned with the impact they are making. They also recycle the old Patagonia fleece jackets.
For awhile I thought that bamboo would be a better choice for say sheets, but after researching the chemical used to produce the fabric; I reverted back to organic cotton. Although I do believe that Bamboo is great for many other applications.