of course La Liga. This league is more technical, players are overally better. Maybe lately La Liga isn't so strong like in previous years, but when we compare results in last 10-15 years in europen competitions like Champions League or Europa Leauge + we will look at matches Spanish team vs English team I guess we will see how spanish teams are overally better.
That myth about Premier League is because there are more big clubs there. But those bigs clubs like Manchester United, Chelsea, Arsenal, aren't as good like in a past. Last season in champions league was an exception. Check even results in champions league this season.
For example 1/8:
Tottenham- Lipsk 0:4 (after 2 matches)
Chelsea- Bayern 0:3
Atletico-Liverpool 4:2 (after 2 matches)
only exception is Real vs Manchester City (1:2 after 1st match).
From Spanish side Valencia's results is pretty bad and Espanyol dissapointed but this team is pretty bad this season. (last in la liga )
I know Spanish teams haven't make good results this season either but still overall Spanish teams show more strength in european games in last decade or more.
Maybe Premier League is more aligned? (Idon't know correct word) but those teams aren't as good as people think.