With the same number of tracks, yes. It's really the width of the track that decides the amount of hiss. So a 16-track 1/2" will basically have twice the hiss that a 16-track 1".
Is that amount significant? Well, it depends on the rest of your equipment. If the amount of hiss on the 1/2" is noticeble together with the rest of your equipment, then yes, it will be significant. Otherwise, nope.
If this happens or not depends not only on your equipment but on what tape you have and if you use noise reduction.
I would GUESS that it isn't significant if you use noise reduction. Then again, with low hiss you might not need the noise reduction, and therefore you can bypass another source of coloring.
Casette has a track width of around 1/32", which is the same as a 16-track 1/2". The noise ration will be higher though, since you don't use teh same medium. The tapes you use on a reel-to-reel have more magnetic particles on them, they are simply thicker. Also, you use a higher tape speed (7 1/2 or 15 ips for R2R and 3 3/4 ips for a good multitrack cassette). So the tape hiss there will be higher because of these reasons, even though the track width is the same.