Frame rate drop vs. regular openFrameworks

[sketch34]

With #define USE_FENSTER: ~170fps
Without: ~215fps

Fullscreen on my attached monitor (1680x1050) with #define USE_FENSTER: ~72fps
Fullscreen on my attached monitor (1680x1050) without: ~120fps

Any ideas why this is the case?

I'm running Windows 7 on my 2011 MacBook Pro (Radeon 6700M with 1GB VRAM).

I've also attached screens of the draw() callstack of regular OF (GLUT callback) vs. fenster. Not sure if that is the difference or not, pretty strange.

int main( ){
#if defined(USE_FENSTER)
    ofSetupOpenGL(ofxFensterManager::get(), 1024,768, OF_WINDOW);
    ofRunFensterApp(new testApp());
#else
    ofAppGlutWindow of;
    ofSetupOpenGL(&of, 1024,768, OF_WINDOW);
    ofRunApp(new testApp());
#endif
}

#define USE_FENSTER
#if defined(USE_FENSTER)
    #include "ofxFenster.h"
#endif

class testApp
#if defined(USE_FENSTER)
    : public ofxFensterListener
#else
    : public ofBaseApp 
#endif
{
...

void testApp::draw(){
    ofBackground(150,38,70);

    ofNoFill();
    ofSetRectMode(OF_RECTMODE_CENTER);
    ofSetColor(255);
    ofCircle(mouseX, mouseY, 10); //mouseX and mouseY are currently not working reliably

    ofDrawBitmapString(ofToString(ofGetFrameRate()),20,20);
}

Fenster

Regular OF