7X50 are best for seeing dim but large objects like nebulae and galaxies. For planets, which are bright but small, you need a telescope. 7x or even 15x is not enough magnification to see Saturn's rings, although Jupiter's 4 largest Moons are easily visible in any binoculars. For Saturn's rings you will need at least 30x just to barely see them. For good views of Saturn's rings you will need 100x or higher magnification.

Those 15×70s should be good. Do you have a mount for them? That will stabilize the image and make things easier to see. A 15 magnification is usually too much for hand-held. The 7×50 will have less magnification. That means that saturn will be a bit harder to see. Don't expect much more than an elongated spot. With a 15x and a mount, you will be able to just make out that there are rings.

7×50's are excellent but they are less powerful than 15×70's and cannot see the rings on Saturn. They are good for starfield gazing, star clusters, and figuring out what that flashing thing is.

You will be able to see the rings on Saturn with a 4.5" Newtonian telescope and a 25mm eyepeice (preferably with a 2x barlow).

A used one will run you $150 for something like a Celestron c4.5" on an equatorial mount.

You may be able to get a decent look with some type of refractor. I know some very nice pictures of Saturn have been taken with 80mm refractors (apochromatic) but the camera sees more than the eye and photos can be enlarged so I'm not sure how easily it can be seen live viewing it in one of those.