The title says it all. I own both versions, but want to abandon GA3 due to VST2 and 32 bit. Is it somehow possible to import the styles from GA3 to GA4 so I can maintain e.g. the comlexitiy control?
Actually: no way. There is also no way to create new styles from scratch.
DeadAgian is right, as long as the question contains the whish for preserving the complexity of styles and since the term “style” is used.
It is however a complex workaround, and that is to record all styles in GA3 and save them as MIDI files and import them to GA4. You will get all the variety/complexity, but as single grooves loadable to pads. Complexity bar won’t work, but everything will be there, fully usable - if you have the patience to do the groove recordings.
Well, this is what I also thought. But … recording all styles as Midi …? 
I have to admit that I am also underwhelmed by the amount of styles included in GA4. Seems to me that Steinberg is geeting the hook on In-App-Purchases when I look at the additional content you have to pay for. 
I do hope that Steinberg will release additional content free of charge.
They won’t as they have released 3 already. GA4 will end up as the most expencive drum software ever if you want a set of grooves to cover different genre. There are no 3. party that (so far) makes any styles, thus Steinberg controls every cent without competition. The styles that Steinberg make will only be usable in GA4 (at least with the complexity function). Grooves that some other companies make are more cross platform, thus utilazation of money spent is greater with other software. And with the limited velocity and some awful samplings in GA, GA don’t get much use here. However GA is for real. If you look to Drumcore 4 it has not been released yet, but they sold the upgrade close to 3 years (!) ago. So Steinberg is better than some, but IMO they loose to Toontrack, Slate, Addictive and Native Instruments. And soundwise everyone loose to MOR, but that requires the heavy interface PLAY - and it has no MIDI player. I am so in love with Cubase 8 but GA4 is an awful product.
Some experiences with exporting Midi Data from GA3
I was still using GA3 in a project, since GA4 is, well, not that intuitive. But this is another story.
Since I have paid money for GA4 i wanted to use the new Kits with the GA3 styles, so I thought it would be easiest to enable Midi Out on GA3 to trigger GA4. … It did not work…
Whatever I tried, I got no Midi output from GA3.
I looked in the manual, and tried every possible Midi setup, e.g. Recording to a fresh new Midi track. Nope.
Then I read that the standalone version of GA3 can export a Midi file, OK, I thought, inconvenient but lets try.
… No Midi File output… Wtf?
As a last resort I changed the compatibility modes of GA3 standalone to Windows XP SP3, and suddenly I got a Midi output file.
tl.dr:
GA3 midi output is not compatible with a 64 bit OS or Cubase version. So be careful when using this plugin.
I can assure you that on my system (see my signature) GA3 is working and sends Midi out.
I just tested it with GA3 driving Addictive 2, it really works but …
-
I use jBridge!
I once tried with Steinberg own vst bridge and though GA3 seems to work you cannot get Midi Output.
But with jBridge, it works. -
In my system GA3 through jBridge curiously does not appear as VSTi!
But it appears as effect!
It means I must create an effect track in order to see GA3 and not an instrument track! -
One must also take care to set the Midi Output of GA3 properly.
It means in GA3 Setup:
Groove Agent MIDI Output must be set to Live to Host
You must also be carefull with the little Midi Symbol (Record to file) on the main page of GA3, when you click this symbol it changes the Midi Output setting in Setup. -
And finally one has to take care of what Midi notes are being send from GA3 and adjust the other VSTi accordingly.
Best regards
Maybe it works with JBridge - but as a PC user GA3 MIDI export is broken - which is a criminal shame and shame on Steinberg for not releasing a patch to fix the issue - It might work in a 32 bit host but since I don’t install the 32 bit versions of Cubase, I don’t know.