you need to understand what makes your tone. when you play live there are 2 considerations: achieving your desired tone, and getting the right mix. for the latter, how you will sound also depends on how your band mates will sound. the audience doesn't hear each sound source individually, they only hear the final result, the mix.
as far as your rig is concerned, it is the combination of preamp + power amp + cab. any and all of these factors will affect your tone.
the hartke bass attack is merely one of the many pedal preamps available. if you are using an amp, the preamp pedal will be in series with the preamp of the amp. even if you set the EQ of the amp to flat, the amp itself will still colour the tone. which means the effectiveness of your preamp pedal will vary depending on the amp you plug it into. that doesn't really help you.
so a preamp pedal into an amp will by no means make your tone consistent with every venue. however, it at least gives you an interface that you are familiar with. this may or may not help a great deal.
i have read many people saying that the cheaper stuff doesnt sound good when it is plugged into bigger rigs or used for recording. thats probably because bigger rigs lets you hear more of your 'true' tone. and you don't really want to hear more of the lower quality stuff. whatever can be considered as 'lower quality' is subjective.
if you go directly into the sound board, you can either consider yourself free from tone-affecting variables such as the power amp or cabs, or you can consider yourself completely at the mercy of the soundman. the PA is obviously more powerful than any rig. since bassists don't drive tube amps as often as guitarists do (some venues don't even use tube bass amps), they may prefer to go DI.
in short, it is just not possible to have the same tone everytime, unless you bring your entire rig to every gig. using a preamp+DI into the soundboard will be the next compromise.
