First. the stainless steel key, is the kissin' cousin of the key I featured in my book - and I rate it one of the fastest keys I've ever used. And a terrific value. Performance-wise these are right up there with my Frattinin Marconi replica and my NATO Marconi key. 

I have not used the Aluminum version; I have reservations because they are substantially lighter, and one of the things that makes the stainless key feel great is its mass. Solid! The resonant "feel" of aluminum is different from steel. So, I didn't find the aluminum version interesting enough to try.

However, although aluminum, the second key on your list has similar design DNA but actually fixes the thing I complained about most on that stainless key: the spring tension adjustment now appears to be keyed to remove backlash - which make fine adjustments difficult on the original, and it adds a locking screw to hold tension in heavy use. Maybe they read my reviews :-) I'm always on the lookout for keys that work for students and experts alike, and at $70, this might fit that bill. So, I'm ordering one off Amazon to try.  

73 Chris NW6V