The most important measurement will be the effective top tube length. Everything else can be greatly adjusted to get the fit right. Just about everyone can fit on TWO sizes of bike. It looks like in that Sportive, you would be on the Small if you prefer the neutral riding position that it offers. If you want the neutral riding position (not aggressive I mean. Saddle maybe a few cm higher than bar), on the R frame, you may need to go with the medium. If you are a new rider, I would assume you aren't looking for too aggressive of a position. If you want the neutral position, it would be the small Sportive or the Medium R possibly with maybe a little shorter than normal. If you want the aggressive position, it would be Small in both sizes. You would probably just run no headset spacers and tilt the stem down on the Sportive which looks cool.

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