Choose leaded Arria II GX for new design?

The aerospace and military markets still use leaded processes a lot, so those components won't be phased out soon. However as you noticed the leaded components are more expensive, and usually harder to order (or at least with longer lead times and/or higher minimal order).

Rework isn't harder with lead-free parts, you just need the right tools and know how to use them correctly ;) And most of the customers (except on the markets mentioned earlier) now ask for lead free products.