I concur with the FWB-300.
You said for mini-sniping, so you are not in a weight limited situation. In that case, the added weight of the 300 will be better for you. If you miss, you can't blame it on the rifle. I have a 12x scope on my 300 and 12x is not enough magnification to even approach the limits of accuracy of the rifle.
BUT (BIG BUT), the FWB-300 is a match rifle, it is NOT a field rifle. As such it is not made to handle the bumps a field rifle will get. Also the trigger is VERY LIGHT, as 10m match rifles have no lower limit on their trigger weight. In the controlled environment of a range, a VERY LIGHT trigger is not a safety issue, as it would be in the field. When I say VERY LIGHT, we are talking ounces, not pounds.
One other thing. The recoiling sledge, which is made up of the barrel, upper receiver, and piston, will recoil and slide backwards about 1/4 inch or so. Some people develop a flinch from having the rear sight or scope physically coming backwards towards their eye. Granted it does not come back as much as the recoil of a .308, but you should be aware of this design. The other 2 of the big 3 have an internal sledge (Anschutz LG-380) or a double piston (Diana 75), so the the rear sight or scope does not move.
Now there is another limitation on these match rifles...the scope, and access to the loading port for your fingers. The scope has to be short enough so the objective bell of the scope does not cover the loading port. Or you get a LONG scope (so the objective bell is forward of the loading port) and put it on a HIGH mount and your fingers would load the pellet into the loading port under the scope tube.
BTW
I have a Daisy/Avanti 853 and 953. Once you fix the trigger, they are VERY accurate rifles, just not a full-on match rifle. But IMHO the velocity is a bit low for reaching out to 35 yards.
Edit
I just saw the Walther LGR was listed with the Diana75. The LGR is in a whole different class from the Diana 75. This is because the LGR is a SSP rifle, not a spring rifle. This eliminates the moving mass of a spring rifle, so as good as the Diana 75, FWB-300 and Anschtuz LG-380 are, they don't compete with any of the match SSP rifles.
