bfr96s vs bfr96ts what are their differences?

if you had checked the datasheets, you would have found out that there is very little difference between them
The significant thing is that the BFR96TS is obsolete

Dave

Since I am not expert, I always need a verification to the things I see in the datasheets.
There might be thermal issues due to the smaller package of the bfr96ts, if these things are driven into class-A.

I believe, RF transistors in this package have been abandoned by all manufacturers since at least five or ten years. Presently you find residual stock at some DIY shops and catalog distributors. If you indent to design with these parts in future, it's time to get your livetime stock now. May be some manufacturers are packaging chips on special request, e.g. as spare parts for military and professional communication equipment.

As far as I see, different manufacturers had BFR96xx variants with slightly different package and slightly different specification. I would consider them exchangeable in a first order, mounting details will probably matter more.

There are many other BJT transistors equivalent (or better) than BFR96 that are still in production:
MRF555 from Microsemi, BFG591 from NXP, or BFG235 from Infineon.
They are available at many distributors as: Mouser, Farnell, or Digi-Key.

I've used recently 2SC5551 from ON Semi:
http://www.mouser.com/Search/Refine....eyword=2SC5551

Here's what a state of the art 100mW 5GHz amp looks like.

http://www.microsemi.com/document-po...5509-datasheet

the mrf555 seems to have lots of guts! 1.5w output, this is a tiny powerful transistor!
My intention is to use it in class-A HF qrp linears.
Thanks!