There are two things at work here, trail and wheelbase.

Trail will increase with less rake, given a head tube angle that slopes back (i.e. 73 deg).

Once you hit 90 degrees, rake makes for negative trail. Think shopping cart wheels - the wheel, pointing forward (backwards) is a 90 degree head tube angle with perhaps 1/2" rake. You push the cart forward and the wheel spins to its "correct" direction, which would be 1/2" negative rake.

Which brings to point, if you have a negative head tube angle, you need negative rake.

Wheelbase - a shorter rake will give you a shorter wheelbase. Wheelbase doesn't necessarily make it more or less stable. However, a longer wheelbase make the bike slower to steer. Think tandem versus BMX bike.

Shorter rake will make the wheelbase shorter. It will increase trail and therefore stability; this means the bike will change direction slower. It will increase toeclip overlap.

cdr