I just got the Curado MGL 71HG. I'm wondering if 20lb(6lb mono dia) braid will be OK for the reel on most applications, or should I go with 30lb(8lb mono dia) braid.

Have you used 20lb braid on a baitcaster?

Nope. Just wondering if it's a good idea. I normally use 30lb braid on my smaller baitcast reels.

I would go 30 if you are comfortable with it. I see no benefit to using 20 lb test on a baitcaster. 

30 is as low as I personally go.  Make sure you wind it on there tight.   Some guys on here use 20 on casting, but the general consensus I've seen over there years is, no lower than 30 or 40.  If you are using a leader, it really doesnt matter.  I have several reels spooled with 50 and all types of leaders and sizes.

   My rule of thumb is .011" diameter (eleven mil) no matter what test they put on it.         jj

30lb is fine in an eight carrier braid. I'm not sure what you're used to, but that reel has a very fast spool. You can fire out a 3/8 oz bait effortlessly with just a flick. Start off with 4 brake blocks engaged and use the external dial to tweak until you get your bearings.