The problem with them for me are:
1) you can buy branded waterproof boots in the sale for not much more. I bought some Scott gortex heater boots for £55 new and they have been brilliant.
2) planet x change their prices with the wind. I’d hate to buy them for £70 to find they are in some wakey sale linked to the number 13 etc. If thyy sell well, then the price might go up. If they don’t sell a lot then the price will go down. I suspect the cheaper £35 shoes have sold more.
3) £70 for some untested boots with no long term reviews are a bit of a gamble.
4} merlin make their own shoes now. I picked up a set of fizik Road shoes for the same price of their own brand shoe and they look identical. Chances are they probably are identical so it’s just about the brand. I choose the bigger brand.
Edit. Have they all sold out or are they just not in stock yet?
https://www.planetx.co.uk/i/q/SHFLRDEF/planet-x-das-boot-extreme-weather-off-road-cycling-boot—2-bolt-spd