For travelling to north india, better to go for 2Ac
But if u r travelling in hwh-mas section, than u can opt for 3ac also. U will not find as such unreserved passengers in 3ac in hwh-mas section. I often travel between hwh and mas in 3Ac of trains like coro, mas mail, src mas ac exp, etc, i haven't seen unreserved passengers as such in 3ac coach in hwh-mas section. Yes u may see 1 or 2 here and there but they doesn't cause any inconvenience as such