Initial impressions from playing several games on each: Iron Maiden is a slow warmup. I started to appreciate it more after about 5-10 games as it took me some time to find the shots, especially in that upper right section. Deadpool was an instant like for me, a lot more accessible right out of the gate. I appreciate the shot geometry on both games and they both take risks on the layout, which is cool.
Both are great, just depends on who will be playing it, what type of player you are, and your enjoyment of the themes/toys. Deadpool is silly/campy/colorful, IM is more serious/shooter focused/fewer toys.