I have trading accounts with most of the brokerages and here are my observations.
L&T, UOB-KH and DMG are using basically the same trading platform abeit with a few visual customisation. The UI is basically the same. With a doubt, the UI is definitely the most friendly and very easy to use. The charts are based on Chartnexus so its rock solid. It also has more data than the free Chartnexus. The live streaming is stable.
I haven't use iOCBC much since its revamp but its definitely better than the previous one. Not sure how stable it is.
DBSV live streaming is iffy at time. The charts are not the best but I really like that you can customise the watchlist in any order, instead of alphabetically order.
POEMS has the worst and most unfriendly UI of all the brokerages and they dun seem particularly keen to improve after all these years.
I mainly use DBSV for my buy order cos the $18 commission for cash upfront is cheaper than most (except SCB which I refuse to use). For sell orders, it either UOB-KH or L&T depending on my mood. I only use POEMS for the Unit Share market.
I dun use mobile apps so the above comments is restricted to the desktop experience.