As for me, currently I use IB. I understand your point. The facts are:
As reported in this thread, execution times and overall order routing quality between IB and Tradier seems to be the same.
pros:
* Commissions. Tradier can save tons of money we spend on commissions;
* REST API in Tradier is much much better than that in IB. TWS API is a pain to work with;
* No intermediate platform in-between compared to ONE -> TWS -> IB Server;
* We can choose a platform that is fully integrated with the broker, unlike ONE / IB which only capable of sending orders to IB and nothing more (and I am not a big fan or using TWS directly to place option orders). So, trading process in Tradier can be more convenient.
cons:
* No Portfolio Margin at Tradier;
* Native Tradier Web interface does not group option legs together in any way;
* As far as I understand, currently they only allow to trade stocks and options on stocks, EFT's and indexes. So the range of tradeable products is quite limited;
* Tradier is a new broker, without historical track record. So reliability and security issues is not fully known at this point.
So, right now I would not rush to open an account at Tradier (actually I can not, since I am not US Citizen). But I watch them closely. For me modern REST API alone is a big plus - if it allows me to easily write scripts to scan for some patterns in options, and there is no limitation of 100 simultaneous realtime tickers as in IB (need to investigate this further), I may consider opening a small account in Tradier to take advantage of their API.