The beguiler will be able to cast a far greater variety of spells at any given moment, due to his spontaneous casting and huge spell list. He has more hit points , can wear light armor, and has a better skill list and more skill points than a wizard. He will be able to act in the surprise round more often than the wizard because he can have decent Spot and Listen skills.
There are even prestige classes and feats that let the beguiler cast spells off his list. For example, a Beguiler5/Mindbender1/Fiendblooded 2 can add any single spell with the [Fire descriptor to his list] So he can add fireball, or orb of fire, and take Empower Spell and now he is dishing out damage like a sorcerer, but with 3 times as many spells known, at character level 8.
A beguiler that wants to have the movement powers of a wizard can simply get a RuneStaff with the transport spells in it and use it via Use Magic Device. Sure, this costs money, but so do all the spells that the wizard has to scribe into his book.
A beguiler will be able to reliably use any wand a wizard can use, plus all the wands that a wizard can't use, because the DC20 UMD check required to do so is easy for him to make.
The main advantages the Wizard has are scroll use plus gaining access to spells a level before the beguiler, who uses the sorcerer progression.
At character level 9, a beguiler can have (12 ranks + 4synergy +5 competence bonus from item) +21 Use Magic Device skill, which means that he is still unable to reliably use scrolls of spells not on his list. I have not found a way to further increase the beguiler's ability to use scrolls, without directly boosting his CHA, which is prohibitively expensive.
Ken
