Almost (not quite) all the "brokerages" offering MT4 trading aren't genuine brokers at all: they're
counterparty market-makers for people who want their own broker to be trading against them and have a direct incentive for them to lose.
I don't, myself, know anyone who makes a living by trading from MT4 (I do know one or two successful traders who
use it, but don't trade from it).
Opinions vary - as on everything - according to the experience and perspectives of the people offering them. I suspect that this is one of those common trading questions to which you can get (at least) two very different sets of answers: there seems to be one approximate consensus of opinion among "aspiring traders" and "traders in general", and another,
very different one, perhaps, among "people who are trading for a living".
NinjaTrader is a whole different world, albeit that the "NinjaTrader vs MetaTrader" discussion is always a huge and complicated one.
These are subjective opinions only, about what suits me and what I like (and I haven't used MT for a while, either, so I'm not "a regular user of both" ... and I'm no "techie" either, far from it, and for both those reasons I'm probably not the best person to answer your question, really!).
Ease of using tick charts, chart appearance and backtesting/forward-testing facilities are really important to me. I won't trade with real money without knowing that my trades collectively have a genuine, proven edge.
It seems to me that everything about NT is far more professional and sophisticated than everything about MT.
Its charts are also far more attractive and easier to read, and when you're sitting in front of the screen for long periods of time, that really matters.
"NinjaScript" is nearly identical to C # programming language, so it's easy to find real professionals to programme things for you if you need to (there's a community of MT programmers as well, but I'm looking at this issue, from my own experience, in terms of quality rather than quantity).
NT's testing suite is far superior to MT4’s strategy tester, and it includes the ability to back-test and forward-test trading scripts even while running a live account.
NT's platform supports simulated data-feeds.
You can also use "Monte Carlo simulations" with NT (that's very important, to me, for testing).
NT's "ATM" (advance trade management) feature is absolutely essential to me. I've lost count of the number of times I've seen people asking questions in forums about "How can I easily do this, that and the other", with large numbers of people chipping in with their comments, replies and suggestions, at the end of which the OP's original problem remains unsolved because he's using MT. It
just doesn't have the trade-management flexibility of NT at all. I want and need
with one click to be able to enter a three-lot trade with different stop-loss and take-profit procedures for each of the three lots. I can do that with NT, but not with MT.
NT supports more chart-types.
NT's standard of technical support is higher.
NT is
far more reliable and smoother-running than MT, which is slow, cumbersome and sometimes crashes.
There are better (I didn't say "more") third-party add-ons available for NT.
NT has a whole range of features (e.g. Projections/Forecasting and Walk-forward analysis) missing from MT.
If it helps/interests anyone,
here's an independent article which compares NT and MT, feature by feature.
To me, it all adds up to the difference between "professional" and "amateur".