I saw some sound person talking about how when you set the eq with the "frown" mid cut it sounds great but in a live mix it'll get your bass lost,I can't prove this as I'm not gigging.
The opposite, when you have a “smile” eq, in other words a mid-cut, it can be easy to get lost in the mix. A frown eq would be a relative mid boost with cuts to the highs and lows which should stand out more in the mix.
With the classic fender style tonestack as used on the terror and AD200 there is an inherent mid scoop. Depending on the context of the mix and cabs used this can work or not work for you. I find layering scooped sounds - like a jazz bass, certain distortions, etc - with a scooped sounding amp and very colored cab gets you a result that is really hit or miss depending on the band and room. Couple that with a limited eq range like on the fender passive tone stack and you may end up in a situation where you’re just totally lost in the mix and there’s no way to correct it.
In this instance as @Wasnex pointed out above an ampeg style eq which has more range of adjustment, or the typical solid state active eq like on the OB-1, may work better for that player.