I have basses with both. They both are great but the Glockenklang is my favorite preamp of all. The Aguilar has a more pronounced affect on the tone, it's own flavor. Some say its transparent but I find a little mid push. And as everyone says, a little turn of the knob goes a long way. The Glock is the cleanest, most transparent pre I've tried. It does not color the tone at all. Just gives boost to the treble, mid or bass. If you like a very "crispy" tone, the Glock's treble frequency is the highest out there, +/- 18b @ 18KHz. I prefer the 2 band that has the passive tone control.