Oscar,
What other calibers do you have? The reason I ask is that if you have anything lighter like a 270, 30/06, 375 H&H, etc. go for the .458 Lott. This would give you a broad spectrum to use. If you don't have anything lighter go for the 416. You can use it for a cross over rifle for the lighter game. I use a 375 H&H for our pronghorn antelope. The females run about 40 kg and it works fine. I think it would be awesome to hunt pigs with the 416.

As for ammunition costs are you allowed to handload in Spain. If you can it will bring down ammo costs quite a bit. At the store ammo fo my .375 H&H is at least $55 for a box of 20. So I have to handload if I want to shoot.