The 7mm-08 has the better bullet selection, you can use heavier bullets,its a short action & performs well from a 22 inch barrel.

The 25-06 is slightly better varmint cartridge,performs best in a longer barrel(at least 24 inches).

I think the 7mm-08 has a slight advantage but with either of then you will not get anything that you already have covered by your 308 or 270.

I own a tikka continental (heavy barrel) in 7mm-08 & just love it but considering the cals you already have I' de look at a tikka in a 223 or 9.3x62 just for somethind different & to cover different ground.