Fighter pilots are not always the best authority on what is preferrable. For example, in the 1930s when open-cockpit biplane fighters were being phased out in favour of closed-cockpit monoplanes, guess who complained loudest? The pilots. Or more recently, when the UK replaced its EE Lightnings with F-4 Phantoms, the pilots complained bitterly because they preferred the Lightning. While the F-4 may not have been the hot-rod that the Lightning was, it was a much more versatile plane, and a much better choice for us than a purely point-defence fighter.
I would guess that there is more than a measure of 'go with what you know.' In their thinking. Not to mention if you going to be shot at, most people would perfer to to be using something their familar (strenghts and weakenesses) over something that is an unknow quality.
I'm not saying it ends the debate, I'm just saying the fact that they would prefer a decades old aircraft is interesting to note. Personally I think we should go for the F-35 - I have more belief with its ability to integrate with NATO systems overall, of which Sweden is not a member, and the gargantuan industrial steam-locomotive that is the United States will keep producing updates and upgrades to ensure that the aircraft will be useful for many decades. In addition, the F-35 has stealth capabilities which the Gripen lacks completely. There were those whom did not want to acquire the F-16 in the 70s for the same reason that they want to go for the cheaper, simpler alternative today. The F-16 has proved itself extremely useful. Also, I don't like companies with a penchant for bribery and corruption - I'm looking your way, SAAB Aerospace.
Stealth will probably be outdated in a couple of decades, and even now stealth capability is only relevant in a first strike operation. Personally I don't want the Gripen. But I really don't want an aircraft the USAF themselves consider inferiour to not only the Typhoon, but the Rafale and Gripen as well. As for the ability to integrate with NATO systems overall the Typhoon is already in service with a number of NATO air forces, the F-35 has a more uncertain future. Potential customers have revived their interest in other types of aircraft, including the Gripen.