Intangibility is better when purely talking about defense. It doesn't get much better than that. However in terms of advantageous, it's hard to say. Itachi's Susano'o not only grants great defense but a Long Range Weapon and Sealing Weapon, also he can still use the defense while employing other techniques, something Obito can not do. Though overall I'd say Obito's defense is more advantageous simply because he can spam it more than Itachi can utilize Susano'o. Similar situation with Sasuke's Susano'o, those this may change with more feats since EMS may allow Sasuke to spam his Susano'o as long as Kamui. Madara's Susano'o is better to me since it seems like he can spam it extremely long due to Senju & Edo buffs.