A VST is not similar to what the Live extension can do. I use redux, but it is always a slightly less integrated experience, as the extension, but extensions at the moment are also not fully featured yet. In short, both have a purpose. I also converted some of my tools to both, by either writing actual MIDI data into Ableton, and otherwise, be controlled by the DAW as a VST; I work on Regroove, which is a Protracker and (Octa)MED replayed library, which can convert from and to several other formats and can be used even in a Drumlogue to playback a .mod as a groovebox like use, with looping, etc.
Renoise is great, but there's usually some compromise like using the tracker/vst's built-in sampler instead an integrated instrument (like Ableton's Drum Rack) or another VST (soft synth, etc)
