Your assumption is that they will migrate platforms and that...

Your assumption is that they will migrate platforms and that clients would be happy for them to.
The recent attempted boycott by real estate agents showed that trying to compete with REA is difficult.
REA has the eye balls and the minutes to almost force listings onto its site.

If i sell my house tomorrow i would expect it to be on REA in order for the largest amount of interest to be generated and therefore hopefully drive buyer competition and the price higher.
If my agent told me he wasn't going to list it on the largest property site in the country he would be fired.
(Separately i do believe that Domain is winning in some of the pricey Eastern Suburbs areas of Sydney. I would expect a property for sale to be listed on Domain).

REA has a stranglehold on the market where by buyers want to go there because all the sellers are there and sellers want to be there because all the buyers go there and that most don't go to the competitors.

Btw I'm not saying REA is going to go straight up to $100 with no consolidation or sell offs. With everything coming out of the company so far indicates that it will get there eventually. IMOH.

If a competitor starts up and promises something revolutionary and has the potential to sink the ship i'll will of course reconsider REA. However currently there is no competitor like that in the market and as far as i can see there isn't one on the horizon.

All the above is my opinion please do your own research.