Lets suppose that we have two OCXO one in 10 MHz and one in 100 MHz with the same phase noise at the same offset.The phase noise is increased by 20log(N) dB) where N is multiply factor. In our case N=10, so we have 20 times larger noise. It meens in simple words that if we create 10 MHz from 100 MHz it will have 20 time less phase noise or if we create 100 MHz from 10 MHz it will have 20 times larger phase noise. It is obvious that when we produce 25 MHz from 100 MHz the phase noise will be less than produced from 10 MHz. One calculation that I have done is that phase noise produced by multiplying by 390 (9750/25) is about 50 times bigger!!!
The ECOC-2522-100.000 existis in various versions with similar prices and different ppB, so a small ppB is prefered as has better stability... PA3FYM AOCJY1-100.000MHZ seems a good choise for GPSDO available from Mouser at half the price.
George, it's 20 dB more / less phase noise. Anyway .. that's exactly why I -from the beginning (end 2018)- beated on the drum concerning PN of the LNB reference and use(d) crystal filters for purification.