Even tho this is a rather snide response... it makes a good point. 35mm and 50mm are pretty close together. And since you already have a 35mm (though you don't say which one), it's possible you'd be happier with the 60mm.

However, it depends. Would longer focal length be more useful to you? Or would a larger aperture that can render stronger background blur be more useful. The 50mm f/1.4 is two full stops faster than the 60mm f/2.8.

A Sigma EX 50mm f/1.4 is also an older design a-mount lens that will require an adapter to use it on an a6000. The Sigma 60mm f/2.8 DN, on the other hand, is an e-mount lens that can be used directly on an a6000.

Sony A600? Do you maybe mean a6000?

Sigma EX 60mm f/1.4? I don't see any of those, either. I do see a Sigma 60mm f/2.8 DN for Sony e-mount. There's quite a difference between f/1.4 and f/2.8.

Sigma EX 50mm f/1.4 comes in Sony a-mount. Those are made for the Sony DSLR models... not for mirrorless cameras like the a6000, if that's what you've got.

Sigma does offer a 56mm f/1.4 DN lens in e-mount.... it's more expensive, though.

On an a6000, if that's what you've got, any of these lenses are short telephotos. The f/1.4 lenses will be able to produce shallower depth of field effects. That can be useful, for example, in portraits... to "separate" the sharply focused subject from a blurred background. Depending upon distance, you can produce some background blur effect with an f/2.8 lens, but can achieve a lot stronger blur with a two-stop-faster f/1.4 lens.

Or, maybe you do mean Sony A600... the a-mount DSLR from 2012, 18MP, APS-C format.

If an A600 is what you've got, then the EX 50mm f/1.4 in a-mount can serve as a short telephoto (nice portrait) lens. There also is a Sigma EX 50mm f/2.8... a macro lens.

I don't find any Sigma EX 60mm lenses. If an A600 is what you've got, the Sigma 60mm f/2.8 DN and 56mm f/1.4 DN lenses won't work, AFAIK. The Sigma "DN" series for Sony are e-mount lenses.

It is possible to adapt an a-mount lens for use on an e-mount camera.

It is NOT possible to adapt an e-mount lens to use it on an a-mount camera.

If you want to start with an inexpensive adapter this one (or something like it) will get you going (manual focus), and then get the fancy one when you have the spare change. Severeal of the adapter makers have units like this. https://www.amazon.com/Fotodiox-Lens-Mount-Adapter-Mount/dp/B003Y2YE5S I think it was $19.95...... I have several of the Fotodiox, they are not top kit, but will do a decent job. I use them for testing different lens that I buy where I don't have the correct body.

On buying from Japan - I have not, but others on UHH have and have reported good transactions, and you are protected by the Ebay protections, which work well.

I did pose a question to Imagemeister on the LEA3 versus 4, as the ads state it will work (I don't have e-mount bodies, just A-mount, but do have a lot of A-mount lenses) hopefully he can clear it up for us.