a 300 atk speed is not a big diff, the adamant bow does 24 more dmg which is better because 300 speed isnt that great. the 300 bow ability will add 300 atk and the mete bow adds 50 atl. the only diff is the nergy which adamant does not give. Adamant is cleary better by the stats.
Its actually 450 attack speed difference, and trust me it does make a big difference. true 300 attack is a nice bonus and can always be used well, but this is really the only plus to this bow besides a little better dmg, all of which is wasted on the speed.
the stats of adamant and mete:
Adamant:
Piercing dmg: 104
Attk Speed: 3250
Bow +300
Mete:
Piercing dmg: 80
Atk Speed: 2800
Atk: 50
Energy: 50
If a weapon is slower than another it had better have a hell of a lot more dmg than the other or it is crap compared to the previous (which is why, for example, the lvl 160 wyrmbone bow is better dps wise than the frozen bow despite its SLOW speed).
The ancient wrymbone does like 130 dmg with an atk speed of 3257.. and the normal wrymbone does 114 dmg and 3257 attk speed. The froz mete does 95 dmg and 2900 attk speed. The wyrmbone does like 35 extra damage.. and that's alot.
I was using the ancient wyrmbone (lvl 160) bow versus frozen bow as an example of one of the only times a slower bow is better than a faster one. the lvl 140 bone bow is equal with the 140, as the dps output is similar and almost impossible to tell apart. Once lvl 160 comes around is the only time you should want to buy a bow after you get the mete bow- which is no longer that hard to do, its harder and more expensive to get the warden bow.
At any rate, I digress. If you all would prefer to have lower dps and spend more money on a bow that isn't that great when frozen is in 15 levels that's up to you. I would still suggest to make sure you don't want anything else before you spend your gold on the adamant bow. Good luck!