C.J.M., trust me, I know where you're at in ife. With over 56 years of very avid detecting, it is very tough to reach the point where I want to hang it up, and I've been at or near that point several times over the past9 years of ailments, injuries, surgeries, and continued pain.... and I had to make an adjustment to trim my outfit to detectors that are light-weight, easy-to-handle, comfortable, and while limited in search time I can still get in 15 to 30 minutes. Painful, but it hurts to do other things as well, so I do what I enjoy.
Detectors: You currently have two models that I happen to like. I ended last year with a brand new Fisher F5 and used a 7" Concentric coil on it which was very comfortable. I lke whatthe F5 can do as it ha more adjustment control than many people think, and the performance is really good. However, in trimming my detector outfit I had to let it go and the only reason was it had a somewhat top-hevy feel at times, and I don't like the headphone jack location. I also have the Simplex +, and for now I kept it in my Detector Outfit, but that's only because I keep the 5X9½ DD, their SP24, mounted full-time. The standard 11" DD is in my Accessory Coil Tote should I need it, but since mounting the 5X9½ open-frame DD it hasn't come off.
I do have my two very light-and-handy Tesoro microMAX models that each keep a 6" Concentric mounted, and I made the change in my primary-use detector which is also quite comfortable, and that is the Garrett Apex with the 5X8 DD 'Ripper' coil mounted full-time. In 2018, March, I tore ly left rotator-cup, then in April, a month later, I had a fall and tore my right rotator-cup and injured my already bad neck. That following August I had cervical spine surgery to take care of a couple of disks and fuse some vertebrae, so after that I started to mend I began trimming my detectors. A little at a time as I thought I might recover more, but I didn't, and won't, so it was time to part with some long-time favorites.
You'll need to handle them a little and decide what is the more comfortable for you, and for what hunting you'll be able to do, then go from there. On my TID units I first grab the Apex, and I also grab my XP ORX which is very light and handy, but while the Simplex + is the heavier of the three, all of them work. Of the two models you mention, they work, but I'd opt for the Simplex +, and in doing so wish you the best of success and also wish you all the best dealing with health issues.
Monte