And assuming you're perfectly happy to contract with a company with a greater than 90% 1 star review rating, per:
https://www.trustpilot.co.uk/review/ee.co.uk
I note your other thread regarding O2 also (that you're not happy with them).
To be honest, I'm not sure there is any best mobile provider now - they are probably all run in the same way. Personally, I had a run in with EE a while ago over something (I wont bore you with the details here), and as such, I will not be contracting with them ever again, in any way what so ever. I only took their 2 month promo SIM as a freebie to use over the Xmas period, nothing more.
I'll give you my opinion on O2 in your other ticket.