The one you know how to use.
I say this slightly tongue in cheek because I have used so many differenent software platforms that sometimes the ones with the latest bells and whistles is not as effective as a "less sophisticated" one you know how to use and dont have downtime learning how to use.
Unfortunately, no one software can really do "it all" Chart, filter, personalised code/filters/indicators, alerts, price, customer service competence.
Eventually, you realize to do everything you want done you have to hire a programmer and have them write your OWN software. Of course then there are data compatability issues though there are ways around them.
Aside from my own software, among the best that I have used (and still use) are:
Aspen Graphics and Insight trading.
First alert almost qualifies but is a resource hog and buggy. JMHO. Maybe use as a back up system?
Both are expensive and from my understanding Insight no longer accepts individual traders. Perhaps you can get a firm to sponsor you. Possible. Also, both are lease only.