Here are my two cents ...
Both guys are decent and love Riddhima truly but for both of them Riddhima is first priority and later comes everyone else ...
Armaan has always been extreme in showing his love towards Riddhima .. Who does a hunger strike these days... Street fighting etc etc .. Will Sid, no both the characters are different .. When armaan returned and Shashank asked Armaan to help sidma's marriage.. Armaan denied saying will only do if Riddhima is happy in that ... Similarly sid wanted to unite AR but as soon as he saw them together he calledArmaan patnichor and wat not because he is human as well he wanted unite them but couldn't take Ridhhima giving importance to Armaan.
Even when after the famous rid's b'day party he wanted to help Armaan and Rids wanted to her duties with Armaan .. He was uneasy .. He was like I can't see Rids spending more tie with Armaan so I have to get a girl for Armaan .. For both of them other person comes after Ridzy ...
Armaan realised only after the tent scene that rids hasn't moved on ... And take her out of the denial mode he turned psychic and obsessive but he has always been extreme case
And I agree that they both should not have carried on the tent scene but they didn't have an ema.. If they wanted they could have done it much before .. Those couple of minutes in the tent was a mistake and there is no doubts about it .. But it was not an affai