Not for me. I am not saying I can play either one of these etudes, but playing that chromatic scale with my weakest fingers(3,4 and 5) is my nightmare. Not saying 25/6 is not hard, but Op.10/2 looks scarier to me.
I think it might be wise to hold off on assigning levels of difficulty until you have spent some quality time with them. They are both devilishly difficult, but think about it for a second...
10/2 has the weak fingers playing single note 16th's while 1 and 2 pluck quarter notes along the way, as compared to 25/6 that has BOTH weak and strong fingers playing 16th's. 10/2 requires a little more in the way of overall hand flexibility, but 25/6 is simply a nightmare of coordination between the sides of the hands. Add to that also is the fact that 10/2 has a left hand part that anyone can play while 25/6 left hand is probably 3 to 4 times more difficult and open to musical expression or lack thereof.
Put it another way... show me ten pianists who can play 25/6 and I will guarantee you that 9 and a half them are fully capable of handing 10/2. Give me ten who can play 10/2 and half of them will likely struggle mightily and never get 25/6.
As for those that 'knew this would devolve into which one is harder'. That is sort of the whole point of this topic - which one should I try next. Difficulty CERTAINLY is a consideration in that question.
To the OP's direct question - 10/4. That is a very well-rounded etude that works multiple sets of skills with each hand. You get some arpeggios from 10/1 (but not a ton), some weak finger work for the right hand (think 10/2) and overall velocity building. 10/1 is a whole lot of the same thing and your left hand will gain next to nothing from it. My vote - 10/4