The Sky Blues kept their hopes of progression to the knockout stages alive with the result - scoring four goals from their five shots in a masterful defensive display.
Arnold says the performance proves the Sky Blues can match it with anyone on the continental stage, and will give them confidence to win their final game against Shanghai Shenhua in Sydney.
"We believe we are as good as any team in the Asian Champions League," Arnold said post-match.
"I couldn't be prouder of the players tonight. They carried out the game plan perfect. They put in a great performance.
"We will strive for the next game to get the right result again."
Sydney FC went ahead in the first half courtesy of a classy Milos Ninkovic lob before Suwon hit back almost instantly through prolific striker Dejan Damjanovic.
Momentum appeared to be with the Koreans but the Sky Blues stuck to their task with skipper Alex Brosque scoring before half-time to earn the lead at the break.
Suwon came out breathing fire in the second half but eventually tired as Sydney FC weathered the storm before striking crucial blows on the break through Adrian Mierzejewski and Bobo.
"We focus on ourselves. The most important thing in my role is getting the tactics right for the players and the players are fresh and ready to play," Arnold said.
"We know Suwon had a game only two days ago and they played Saturday in Jeju. We felt they would be tired for this game tonight.
"My boys played in Perth on Thursday - they were in great shape mentally and physically."
To progress to the knockout stages, the Sky Blues need to defeat Shanghai Shenhua at Allianz Stadium on April 17 and hope Suwon lose or draw against group H leaders Kashima Antlers.