Weir meanwhile made his third career appearance off the bench against Ireland, replacing Jackson at fly-half as Scotland hung on for a 12-8 victory at Murrayfield.
Townsend himself battled with Craig Chalmers for the Scottish No.10 jersey during his playing career and he believes the differences between Jackson and Weir are minimal.
"Duncan now feels much more confident about where he is," said Townsend. "You just have to make sure they are improving and taking their opportunities when they have them.
"Ruaridh took his opportunities leading up to the Six Nations very well in our games against Edinburgh and over at Castres [in the Heineken Cup] as well.
"It was difficult at the weekend. Between them I think they got 12 touches of the ball, and I've seen stats from games where the stand-off got 50 or 60. It's hard to get into a game when you're mainly defending.
"I disagree with the caricatures of them. Both have strengths and both have areas they are working on. It's definitely not as simple as saying one is a kicker and the other attacks better.
"Duncan's attacking game is really improving, his running on to the ball and his passing; while Ruaridh's kicking game has always been there. He has the length and it's just about making sure he kicks at the right time."