Sumwun,it's still my personal opinion but flygon is better because of its dragon typing.Excadrill has many weaknesses but also many resistances.While krookodile has almost no resistances.Krookodile,being a dark type,is supposed to take out the psychic and ghost e4.but alas! All of them have either grass knot (and dam boi krookodile do be fat) and energy ball (great move).while no Mon should survive a hit from krookodile,if one does,a grass knot or energy ball can greatly damage it.While flygon can learn crunch and fly (honestly speaking flying types are mostly bad so,having a non flying type be able to learn it is a great deal) ,moves that are effective against 3 e4.Excadrill can learn x scissor which is effective against 2 e4.and however,excadrill is weak to focus blast which is a move most the psychic and dark mons have.But flygon is only weak to sigyliphs ice beam.And other than that flygon has great stats,good for attack and ok for special.It also has a good tm move pool.