... let me tell you a story...
I have a PCB which has two I2C devices on it and some pull up resistors from SCL to VCC and SDA to VCC. I picked 47k as a value for the pull-ups

Now to test the set-up I have been using an Arduino UNO (effectively a AVR 328P) using the 'Wire' library which uses TWI and turns on the internal pull-ups which are around 20k.
Testing (100kHz) shows that almost always I see the device nearest the UNO; the further device only appears sometimes.
Now I am assuming this is because I was wrong in picking 47k? But why?