Let's compare the BattleAxe and the LongSword. The Axe does 1d10 damage and has a +2 to-hit. The Sword does 1d8 damage and +3 to hit. They are otherwise functionally identical.
The question at hand is whether +5% chance to-hit is worth about +10% damage. I think the answer is "yes". If the question was purely based on doing basic attacks with no bonuses, the axe would be superior, but there are other factors. For example, a typical fighter will start with a strength bonus of +5. This means that the Axe does an average of 10.5 damage and the Sword does an average of 9.5, bringing the percent bonus to damage to less than 10%, but leaving the to-hit bonus at +5%. As the character reaches higher levels, this factor becomes even greater.
The other factor is that damage isn't everything. Almost every attack grants some sort of advantage from hitting the enemy. That +5% chance to-hit doesn't just increase the chance of doing damage, it increases your chance of getting that secondary effect, which, particularly with Encounter and Daily Powers, are vastly more important than the pure damage output.
Yes, I am aware that the percentages I quoted earlier aren't true when you're talking about Encounter and Daily Powers.