Not the same.. belle saison is from a brewery in Belgium, and 3711 is from France (Brasserie Thiriez). They are quite similar, though. Agree on the underpitch, I like to underpitch and hit it with extra oxygen.
Edit - belle saison tends to give some peppery lemon notes when fermented warm, like above 70°F. At lower temps it's pretty clean. 3711 gives similar pepper and citrusy flavors at lower temps (under 70°F) but can start throwing a lot of isoamyl acetate when you ramp up the temperatures. I'm personally not a fan of the banana runt flavors, but it makes a great saison at lower temperatures.