Leasing fighter jets is very difficult decision to make. All that experience will have to be surrendered, so it should be a lease + buy deal, so that the jets can be bought after the lease period is over.
But it's a much cheaper option than buying outright with our current economy. And the navy will get modern jets quite a few years before they originally planned to. It's interesting how the numbers have fallen from 80 to 57 to 36 to 18 since the requirement first came up the previous decade. I'm sure an extra 18 will be added to the lot in a few years.
Anyway,
@Falcon is talking about something else actually, a mix buy of SH. But that won't work out for the IAF. The requirements, as I've said before, are totally different. SH doesn't meet the IAF's requirements, or else they wouldn't have rejected it 10 years ago. And you can be doubly sure the requirements today are even more difficult for the SH to meet. And if interoperability was the main concern, then the default option would be choosing a jet that's already in the IAF's inventory, the Rafale. So the IN's decision has nothing to do with commonality since the IAF's decision is still pending. The IAF can't make a decision to buy 150-200 SH simply because the IN has leased 18 of them, that's completely illogical.