I've used both Aluminium and Steel Cross bikes in the past, and found the Alu one to be much more comfortable...
Now, with the production of Metal Matrix, Titanium, Carbon Fibre, Magnesium and countless other materials, which do you think is the best for cross.
Me personally, I'd go for Titanium, especially the new Morati or Seven framesets that have recently come out

Cheers..................................Rich