The Roubaix Comp has what I would call recreational geometry, with a short reach and tall stack, to produce a more upright riding position.
Here's a link to the geometry chart.
https://www.specialized.com/us/en/ro...=240093-129154
The smaller size has 6mm less reach and a 10mm shorter stem, so total reach to the bars is 16mm shorter. The stack on the larger frame is 21mm taller, so the bars should sit significantly higher. Whether that's good or bad depends on your body proportions. To get an idea of your proportioning you need to determine an accurate saddle height.
There's a big 41mm difference in seat tube length, which makes saddle height more important to know.
Cycling inseam is measured from the floor to firm crotch contact, in bare feet. As an example of an extreme, I'm only 5'-6.5" tall, but my cycling inseam is 32-5/8" or 83cm and my saddle height is 73cm. I've seen people who are 6" tall post the same cycling inseam.
Unless you have very long legs, like mine, I'd lean toward the smaller size, because the bike has such a tall stack height. Even then, there's no reason you can't put a 120mm stem on it to increase the reach.