Aluminum rods grow with age and use and have to be re-sized every 15k miles or so with street use. What a pain in the a*s ! They can be resized about 5 or 6 times then you will have to throw them away. I have said this before , listen to your custom engine builder. Most times they really know what works because they have been there. Most times they don't know how to read those hot rod magazines that get 90% of enthusiasts (myself included) into trouble.
If you haven't got your crank yet I would also look at the so-called Chevy setup. Smaller, lighter , cheaper rods, smaller rod bearings means more power. If your builder is worth his salt he will know what I am talking about. It will cost a bit more because of the higher crank cost but it is worth it.
I don't know much about titanium rods other that a few years back they were used to build Nascar qualifying engines. Seems they clearanced the bearing really sloppy for more power and the rods would hold together long enough to qualify the car without stretching. Today they are illegal to use I think.( I don't know) I hear that they have similar propertys with aluminum rods. Maybe someone else can tell us how they fatigue along with their propertys. I can tell you, titanium normally has low lateral strenth. Like a pensil it will snap in the middle easy but has superior strenth when compressed. (like on a rod)
Now repeat after me. STEEL RODS, STEEL RODS, STEEL RODS.
COBRASHOCK