Based on the bikes you listed, I assume this Spain tour is not loaded. A vehicle will be carrying any gear. Overnights will be at motels. Spain has mountains and lots of little roads that were just thrown down on whatever ground was there. Meaning they are steep roads. Gears as low as possible will be appreciated. Even if you are not carrying any gear. Pretty sure the low gears on all of these bikes can be lowered by putting on a new cassette. 32 or 34 tooth rear cog. And the triple crankset bike can have the inner chainring changed to a 24 tooth. Compact cranksets with a 34 chainring and 32 or 34 rear cog will get you a low of about 26 or 28 inches. Low enough. The triple will get lower.
Trek or Specialized, either side of a coin. Both are large conglomerates making most of their bikes in China. Both use the same parts from Shimano to equip their bikes. The bikes you listed are 8, 9, or 10 speed cassettes. Sora, Tiagra, and one grade lower than Sora are the derailleurs, shifters, cranksets, brakes, etc. I suspect all will work OK. Never notice much difference. 8 and 9 are kind of older technology now. Parts are still available. But 10 speed is more current Does this make a difference? Probably not. The most expensive Specialized bike has Tiagra 10 speed. So its parts are higher end than the other bikes. Thus it costs more.
