How much TIME do you spend editing styles & sounds on your arranger? As much as necessary.
Lets get realistic here. Most performers use 10 to 15 onboard styles at best, and some performers, particularly those that use lots of SMF files and MP3s, use even less. The vast majority don't know how to tune styles and SMF files, and for the most part, they don't care to crack an instruction manual to find out.
Most days I use a mix of onboard styles and third-party styles, all of which range from good to excellent. The manufacturer doesn't dictate which style to use, or how it sounds--YOU DO! You have all the controls at your fingertips--it's just a matter of learning how to use them to YOUR advantage. If the styles and midi files sound good to both you and your audiences, that's all that matters. If they don't sound good to you or your audiences, open the instruction manual and learn how to use the keyboard's onboard programs and features.
Gary
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PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!
K+E=W (Knowledge Plus Experience = Wisdom.)