is it better to buy MP shoes (20 MP) or Blasting Wand (40 AP)?

I am talking about for the initial fight at top tower and I am wondering strictly from a damage stand point. I know that shoes being faster help.

Well the shoes obviously if you're running pen reds.

It completely depends on the effective AP ratios of your skills.

generally speaking, I think you're better off getting prospector+boots rather than boots 2 or boots + wand. The mp5 is important to some champions, and the 200 health is very significant as well.

why is that?

Probably because it would give you 20+9.5 (10)= 30 total mpen, giving you true damage.

but that doesnt mean the dmg output would necessarily be better than just adding more ap to the skills. there is no 'obvious' answer, someone just needs to do the math on this one.

another possibility to get some survivability in there: start with boots, ruby crystal, amplifying tome- after the first battle turn tome and crystal into haunting guise and that frees up boots for ionian or merc treads

Flat reds gives 8.5 MP, with your boots its 28.5 MP. They have 1.5 MR, which you can p retty much say your doing true damage to them. Your abilities scale up as you level up so in turn you do more damage than simply having 40 more AP, since 40 AP doesn't equate to 40 more damage due to your AP ratio scaling + their MR resist knocking it down further. Also its not a bad idea running boots 2 on bot. Ran Sorc boots 2, on fiddle and just true damage drain the **** outta whoever I am against. The speed to get close and to get away and MPen for the damage, since fiddle gets -10 MR shred for free.

Also depends on if you need ionian boots to deal consistent damage (Lux comes to mind)

Flat MPen is more effective imo against opponents too stupid to ever build any MR.

It becomes less effective against opponents who do, because you will eventually have to get a Void Staff. (40% Magic Penetration also means any flat Magic Penetration you've racked up becomes 40% less effective.)

Though there's nothing wrong with having both flat and % MPen if you're able to do so without making large sacrifices in AP. (For example, there's little reason to not get Sorc Shoes because the only other good boot choices are CDR Boots or Mobility Boots)