I watch anime in both dub and sub..... so don't judge. Though I will say this.... the English VA for Bleach and Death Note did an outstanding job. Tokyo Ghoul in English and Japanese.... eh..... I'm kinda in the middle regarding both versions. Attack on Titan is fantastic in English IMO (even though people like to shit on it.)
Gintama is only good subbed. The dubs they put out are shit, because well... they don't cast British VA and IMO the only VA suited for that would be British VA. But of course England doesn't make dubs, so that's a given I guess.....
It's just I can picture everyone in the sub speaking with various English dialects. Such as Kazuya Nakai (who usually has a Kansai accent) having more of a Cockney accent in English.
I suppose that happens when you read subs I guess. You can picture people's voices in your head.
Regarding Code Geass.... definitely sub, since the plot revolves around Japanese rebels against the British imperialists who occupy Japan..... 
Also I'm currently finishing up Nichijou, and I'm sad it's starting to end. Because I want MOAR!!!!!! 
Finally.... Berserk 1997 is awesome dubbed. But IMO the 2016-2017 anime is better in the sub.... maybe it's because I like Hiroaki Iwanaga's voice for Guts.
