I have the 300s and I do love them. Here are the pros and cons, as I see it:
Pros (300s): The android device is the control box for the glasses, therefore you don't need another device. It supplies the power to the glasses. The software that runs in this is optimized for the glasses. It does support bluetooth connection to keyboards and mice, so you're not sidled with the touchpad (which takes some getting used to). When you're flying, you don't need more than the glasses.
Cons (300s): The hardware chipset is older and therefore will eventually become obsolete. The hardware tends to heat up and some people have reported black outs when it overheats (I haven't had that yet). You are limited to the software that's in the
Moverio store (but you can side-load other applications...you're kind of on your own for that). The controller is the only android device that the glasses can be used with. If you want someone else to see what you're seeing when you're flying, you have to hook up some kind of kludgy mirroring option that usually has some kind of performance problem.
Pros (35E): You can use the glasses with any device that supports the HDMI output. That means you are "future-proofed" because you'll be able to use them with future devices. This also means that a more powerful device (that won't overheat) will be able to be used for your drone. You are not limited to the applications that have been selected. Someone else can look over your shoulder (to your cpu device) and see what you're seeing through the glasses.
Cons(35E): You'll need another device that will actually be your cpu and source of video. You'll need power for the glasses. You have an additional box to add to your rig. It was a positive too, but for privacy it's a negative: Someone else can look over your shoulder (to your cpu device) and see what you're seeing through the glasses. The price point for the 35Es doesn't really support the fact that these are the 300s without an android device - you would think the cost should be less by approximately the cost of an android phone...but they are actually priced about the same as the 300 (with an android device)...so that's a pricing decision by Epson that puts it in the "Cons" category.
Conclusions:
Since I already own the 300s, I am looking to combine the two in the future. My upgrade path is to get the 35E interface box (only) and use my 300 glasses with them - once that option is available. That will give me my future proofing. If I was buying brand new today, I think I'd go straight to the 35Es and get a
crystal sky or some other device as my cpu source.