Your hobbies will most definitely suffer during medical school and likely worse during residency. It will not be as noticeable if you are single or without children--but a big chunk of your free time will be absorbed by classes, labs, rotations, and constantly feeling that there is more material you could study. In residency, depending on your specialty, you could be spending up to 80 hours per week (possibly a bit more) with clinical duties, and then a few more hours each week with studying and performing logistical details like applying for medical licenses, completing credentialing forms, etc. If you do the math, that doesn't leave a lot of time for hobbies.
Once you are done with training, which is a minimum of 8-9 years out from where you are now, you will have more control over your time--if you choose a specialty and practice environment that affords you that luxury. For instance, with my own specialty of anesthesia, one advantage is that when I leave the hospital, I am DONE. I can devote the rest of my time to whatever I want without being tethered to the pager or typing notes at home after clinic. If you are one of only two OBGYN docs in a rural town, that's unlikely to be the case.
As others have stated, you have to decide how much your free time and ability to pursue your hobbies is worth to you. If you commit to becoming a physician, you have to accept the fact that for the next 8-9 years (minimum), you will have far less time of your own--and that there will almost always be more material you can study or more time you can spend at the hospital. You may have better ability to carve out time for yourself after training, but that is almost a decade away for you.
I can't speak for the educational process of physician assistants personally, but it is certainly shorter in number of years--so you will be out in practice quicker. And in general, PAs have more protected time out of the hospital once in practice--but they, too, are often burdened by the duties of call.
Ultimately, it's your choice. But just keep in mind that during medical training, you own very little of your time. And at the end of the day, there are very few clinical jobs (even aside from being a physician) that are truly "nine to five."
Good luck!