If you are looking to wire in SGD, the most reliable choices are indeed Coinhako, Coinbase and Gemini.
I personally haven’t use Gemini but can give you a quick overview of the other 2.
Coinhako:
- Used to have their own bank transfer mechanism which was a huge plus given that Xfers is almost always down
- Coinhako prices used to be a tad lower than coinbase, so it always made more sense to buy on coinhako. I believe this is still the case, but the difference is pretty small now. (Transfers in and out of exchanges always took awhile, so little to no arb opportunity there)
- Secured with BitGo (a very popular Bitcoin security / multi-sig wallet provider)
- Appears to be insured
- Traditionally had a higher availability than Coinbase
Coinbase:
- Probably one of the largest exchanges around
- Operates their own exchange called GDAX
- Well funded startup
- Tends to list higher prices but in practice they work out to be the same
- They say they store parts of your currency in cold storage (which means not connected to the internet)
- Has a credit card option (can sometimes work out)
- Used to have a bad reputation for being down / unavailable quite a bit
- Only has xfers as an option if you want to deposit fiat currency
Overall, both are solid, I ended up buying most of my stuff on Coinhako because xfers was always down. However, now that they both use xfers exclusively. I don’t see much difference. I think it just boils down to whichever you can finish their KYC steps faster. I think coinbase might technically be safer if they really store your currency on cold wallets. However, the long term goal is to move your currency offline (I hope).
Hope that helps.