I've been using both for quite a while now and I think they're great. As has been said, you can specify if you want to play it safe or be a bit more daring & fashion forward.
You can also ask to change stylist if you think the person who made up your box hasn't quite connected with what you're looking for. You can add an update any time before the box is made up, letting your stylist know if there's anything in particular you'd like to see. I'm looking for midi skirts just now so that's what I asked for. You can specify your price range, too.
One thing I will say - StitchFix are developing their own brands and 3 of the 5 items in my last box were their brands. I wanted the boxes to see a wide range of brands, so this concerns me a bit.
When you set up your account and profile you add in your preferred card details so, when you get your box and choose what to keep, you can check out easily. This also gives you the opportunity to give feedback on each item, eg price, quality, fit, cut etc to help your stylist with future boxes. You can also vary the frequency of the boxes from monthly to bi monthly to quarterly or just on demand. This can be done at any time.
Lookiero give a bag for returns and with StitchFix you re-use the box. I use the Hermes option and take my return items to the village Co-op, where the Hermes shop is.
I usually keep at least 2 pieces and on a couple of occasions I've kept all 5. The stylist £10 fee is deducted from any purchases and if you keep all 5 pieces you get 25% off.
I've got quite a good rapport with my Lookiero stylist but I've just asked to change stylist with StitchFix. I'm disabled and find getting out clothes shopping night on impossible so I find the services invaluable and I always look forward to receiving box. Please shout if you have any questions or would like an introductory code.