Some info...
I've had 2 now. The first was estrogen only, the second estrogen and progesterone.
I used to use patches, and there's no comparison to implants. I've never tried injections so I can't comment on that.
I wasn't getting very good blood levels with patches, but although its still early days its looking really good with the implant.
My endo told me that once I got past the first implants it might be up to a year between implants. That would be awesome if it happens.
If you want to see what they are inserted with look up "trocar", but definitely not if you're afraid of needles. It doesn't hurt as you get a local anesthetic first - that stings quite a bit. Once the local did it's work all I'd feel is some pressure. It minor surgery so after the local wears of there's some pain for a 2 or 3 days, and you need to be careful of for a week or two (I forget exactly). Its not serious pain, but I remember I had to be careful moving about and how I lay in bed at night for a few days. I get mine put in high up on my butt, alternating sides each time. After about 10 days the stitches need to be removed. I've had them removed by a nurse at the local doctors. I'd do it myself, but I can't reach. All together its pretty minor in the long term, and you soon forget about it.
I asked about the size, and was told 4.5 mm diameter for estrogen and 3.5 mm for progesterone. Not really grain of rice size, assuming I'm not confusing the length and diameter. I wasn't brave enough to actually look though. Maybe next time.
I've a bit of a phobia about injections, and its the local anesthetic I find more disturbing. No idea why. I think I'd have a real problem doing my own injections every two weeks.
I travel a bit and I don't much like carrying medicine though customs - and that's without syringes.
I don't really like taking so much medication each day - its a constant reminder of what I'm really doing, and implants also help with that.
I'd never want to change to anything else now. If you can get them then definitely do. I think if I had to I'd get on a plane and fly overseas once or twice a year for this.