Warriors went over for three first-half tries through Sione Tuipulotu and a double from Johnny Matthews but were forced to defend for long periods after the interval and missed out on the score that wold have given them the bonus point.
Speaking to BBC Scotland after the match, Smith said: "The Stormers are a class outfit. They've played in the final the first two years they've been involved [in the URC]. They were leading the table with two victories and a lot of points scored so we always knew it was going to be a tough one and it was important to get the victory.
"From a coaching perspective you always want a little bit more. I think we were good enough and created enough opportunities so that is a regret, but it is something that will motivate us going into this week."
Smith praised the contribution of free scoring hooker Matthews, who was called into Scotland's World Cup squad and marked his Scotland debut with a try in the win over Romania.
"He's got some excellent attributes and he's added value again," said Smith.
"His first start of the season and he's proved why he was called up to the Scotland squad. He's still a humble guy, still got his feet on the ground but he's obviously hugely motivated to get another go [at Test level]."