Hmm good question. I'm interested in the answer myself. I've tried quite a few things and haven't found one that I really like yet.
I have tried the vac-u-lock system which didn't work that great. We have a couple of dildos for it of various sizes. The dildos do stay put and they have some that look slightly realistic more than most. The problem I have with it is that I really can't get enough thrusting power so I end up holding the dildo and moving it in and out with my hand not my hips. The harness they give you is just not snug enough for continuous hip thrusting action if you know what I mean.
Then I got another one which I can not remember the brand name of. The harness fit a lot better as it had a buckle not just snaps like the vac-u-lock had. It had optional double penetration for me. It worked well the problem was it didn't look at all realistic. I want to look down and see that I have a cock. So I lost interest in that as well.
Then my partner bought me a feeldo with a bullet vibe thinking I would like it. First off not at all realistic so points off there. Second it's extremely heavy and probably because I had kids it doesn't stay inside of me. With an o-ring harness it's work all right and does actually feel quite good to me. The sensations and the rubbing does as advertised. Still it's not meant to be used with a harness so it's a bit awkward. We continue to use it but I'm saving up for something new.
Which is the Goodfella.
http://store.babeland.com/dildos-silicone/goodfella I really like this because it does look more real and the real looking and feeling balls are a huge plus to me. They say it can be used to pack as well if you don't mind walking around with a hard-on. There are is no stimulation for me with it apart from the visual but I can always use a vibrator for that. You do need to buy a harness for it if you don't already have one.
Good luck. There are flaws to all of them. I hope you find one that works for you.
