Which is better for a 24 year old gay guy, to live in Stuttgart or in Heidelberg/Mannheim?

Which is better for a 24 year old gay guy, to live in Stuttgart or in Heidelberg/Mannheim? I'd like some details about the gay nightlife(bars n clubs), people(approachable or reserved; when you're at a bar, club or a park would people approach you like I experienced in Brussels, Belgium), green spaces n nature, architecture, gay events, festivals, associations, n get-together.. More information is very appreciated.