VG1 Sanmai is a 'stainless' and said to be close to 440C. Slightly better than 440B/AUS8, does not quite hold its edge like VG10 but is tough.
O1 is a oilhardening tool steel. It will rust easily when left wet and used in field, but is tough. It's easy to sharpen and will take a really sharp edge. Edgeholding is like VG10. I like it because it's easy to sharpen and strop but it does rust pretty easily - you have maintain it.
If you're gonna just put it up on the shelf and check on it regularly (and oil it), O1 looks like a better valued buy.
If you're gonna use it out camping but will baby it and oil it, O1 still looks like a better valued buy.
If you want less maintenance than a stainless would be a good option.
Steel performance is highly dependent on the heat treat. Good heat treat can make a lesser steel perform well. Cutting performance is dependent on edge geometry, user skill, and steel performance.
Looks like you know prices already and can make an informed choice.
USD has increased in the past 6 months, some local sellers who are still selling at old prices are worth looking at.
If you're looking to spend USD400 on a cold steel, I would ask you to consider looking at handforged customs. I know it looks like a plug but look at the sanmai Claudio Sobral/CAS recurved hunter I listed for sale for eg. It costs a bit more but you get a handmade, handforged knife that will give you more 'soul' than a factory made cold steel - can't say anything about performance though - I do like the performance of cold steel (well at least when I first started out) especially due to watching those tacky but entertaining videos