Depends on what you're wanting out of it. Extra long so that you BOTH can use at the same time? Is that why you're asking about extra long or double ended? Or are you asking which would be better stimulation wise (using one person at a time?) First of all, if you plan to share it, only use silicone or glass or steel. Something non-porous that CAN BE BOILED/STERILIZED. That would be your most important thing to look for, if you do indeed plan to share it.

Secondly, good luck finding a double ended dildo that is not jelly. Which brings up a question I have never wondered before. WHY the heck do they make most double ended dildos JELLY?! A porous material? Wow. That just occured to me. OK sorry.

Anyyways, EF does carry glass double ended dildos, but they're mostly for using on ONE person at a time and are only double ended so that you can switch ends. My double ended glass dildos are not near long enough for 2 people to use at one time. I believe my longest double ended dildo is the Pink Passion Wand. It is still not long enough to go inside me and someone else at the same time.

Here is a long enough double ended dildo for two partners to use at once, BUT it's not a safe material to share. Pretty Pink
Here's a photo of it:


Go to EF's search bar, type in "double ended dildos" and you'll find a lot of double ended dildos designed for two people to use at once, but they're mostly jelly. So unless you are OK with sharing something that cannot be fully sterilized and all that, then you may want to dig deeper.

Gel Veined Double Ended Dildo


This one I believe is safer than jelly material:
Mini Double Dong


Feeldoe gets nice reviews, but it's strange and hard to explain. YOU can check it out here though: Feeldoe



Here's something totally safe that you might could use. It's steel and expensive, but gets good reviews.
Metal Worx Curve

And there's the "share," which can be shared and is silicone! Yay! There's also share Large, you might wanna look up.
Share


Hope some of this came as helpful to ya. If not though, definitely type in "double ended dildos" in the search bar up there. You'll find a lot of things that fit what you may be lookin' for.