I and others have answered those questions fairly well here ->
Should I buy an original manufacturer battery, or is a generic brand OK?.
I just looked through my prior answer and I think it covers the subject fairly comprehensively.
A couple of specific points related to your questions:
(1) Clone batteries often claim higher or much higher mAh capacities than genuine originals.
While in some cases modest gains in capacity MAY be genuine, very large ones invariably are not, and a clone battery will usually have a lower capacity and shorter operating life than a genuine one.
This does not mean that they are necessarily lower value-for-money - see my answer cited above for more detail - often the overall cycles x mean capacity / Purchase_price will be better or even much better for a clone. I would tend to avoid clones that claim substantially higher ratings than original batteries as, once a vendor is willing to label batteries with manifestly incorrect technical data their integrity and all other claims are suspect.
In this case the 91% increase in capacity from 1020 mAh to 1950 mAh is in-credible.
As opposed to clones there are outright fakes such as
Update on fake NPW-50 and
(You Tube 3m-19s) How to tell if yourebay Sony battery is fake
You might think that a fake-maker would try to do a good job so that they can commend a high price and continue to be able to sell product, but the usual experience is that fakes are bad or very bad performance wise.
(2) The 7.4V versus 7.2V claimed difference in voltage is meaningless. Lithium Ion cells have a fully charged voltage of 4.2V and voltage at end of discharge is about 3V (set by low voltage cutoff in equipment). The "average" of 3.0 and 4.2 is (4.2 + 3.0) / 2 = 3.6V. However, the discharge curve is not linear and actual voltages are affected by load current so stating 3.7V or 3.6V as average voltage means nothing. 3.7V is arguably closer to the average for a lightly loaded cell but 3.6V is probably more commonly used.
Update - April 2015:
I just bought 3 x clone batteries for a Sony A77. They all worked OK at first but after 5 to 100 photos taken all 3 cause camera to give a "incompatible battery message. I have used MANY clone batteries with a range of Sony and a few other cameras and never before seen this happen.