Think this is a very good signing.
Is he better than Ota. -Damn straight he is - quicker, not as rash in the tackle, reads the game better, distribution is better and better 1vs 1 - based on that alone he improves the team.
As others have alluded to he could play left back as a push (which means he is already better defensively than Mendy!)
Also he has leadership experience - something none of our centre halves have at all
Now Stones might be the one to also make way but it could also be Garcia. AS good as he is Im just not sure he is cut out for the run of the mill premiership week by week as he lacks pace, strength and height which is something that is needed (Im also fully aware of the many strengths/postives Garcia possesses).
Laporte, Ake, Stones and Koulibaly would be 4 very strong centre halves
Laporte Ake ,Garcia, Koulibaly would also be 4 very strong centre half options.
And at 41m thats a steal compared to other prices we may have had to pay previously for the likes of McGuire (75m?)