I have had more luck with DOI but I have only been in the game for a few months.
So what´s the opinion of the big players?
It all comes down to CVR and EPC. To me it doesn't matter if it's DOI or SOI.
There are a lot of DOI offers out there that actually convert better than SOIs, so it's good to test a bunch.
The only thing is sometimes DOIs can allow you to stay on the offer longer as obviously the emails are confirmed.
Other than that though the only consideration I make is CVR and EPC.
I prefer DOIs personally, mainly because of what jabong82 already mentioned ... less quality problems.
But yup, it all comes down to testing, both can work and I doubt there is a clear winner here.
SOIs are easier to test, DOIs can last longer ... if I was to give you any advice on this at all, I'd say start testing with SOIs and once you know you where the quality traffic is, try to target it with higher paying DOIs.
Thanks for your replies.
Are you guys aware of any hybrid style offers?
Where you get a small fee for a signup and a recurring commission.
This is quite common in the gambling sector but haven´t came across it in the dating sector.
Who's got the best SOI dating offer going right now for tier 1 geos? :-)
)Whatever you promote, SOI or DOI , at the end it boils down to the amount of sales the advertiser gets from your traffic.
If the advertiser doesn't get sales, regardless of DOI or SOI you will be kicked out of the offer.
So ideally you want to promote CPS to avoid quality issues. If that's too risky I would fall back on DOI.
I think you've got it pretty much covered by previous commentators, but just to share from our side - one of our VIP affiliates mentioned to us that DOI offers were performing better for him, even when he was just starting out, being a complete newbie.
Normally we'd recommend SOI for beginners, but he was brave enough to go where we didn't advice, and he got a gold mine with fewer competitors
After all, you never know until you test it with your traffic.
Thanks Matuloo
We recently launched a bunch more new offers and landers in VIPoffers so if you need something new and fresh that converts hit me up
SOI is good too. Especially on tier 2 countries.
You can try your traffic to convert on our Dating offers in Affmy 
I prefer ZOI. Zero Optin. My personal fav.