I really think this is the case of their website design not giving a feeling of quality... Their design is OK... but I bet if they could give the site a softer look and have it convey a feeling of assurance/reliability - they'ed have a much better product... I realize design is a small part of the equation, but it goes a long way in gaining trust in the brand... Right now their site gives me the feeling of "stodgy corporate", slightly sketch... they need to fix that... stripe in comparison gives me the feeling of "cool", "reliably", "smart"... i'm just one dude though... who has been regrettably using authorize.net - so take it with a grain of salt...
There's nothing wrong with Authorize.net. Well documented, easy to implement API, automatic billing or charge-by-reference, reliable service, not overpriced... Why would you regret it?
As my service has evolved and newer payment options have emerged braintree, stripe... I'm just probably jealous envious of the coolness of those services... but you're right - authorize.net has not yet failed - good point.