I've been trading equities for a long time. I've also been reading Elitetrader for a long time. Somehow I've never felt compelled to give my option of which moving average is best or which candle stick pattern best reflects a reversal. But software choice is very important. Living in a house with traders, after all, what do engineers and computer scientists do for fun? We've been through a lot of software.
I hate the question, "What's the best trading software?". That's like what's the best vehicle to drive to work? In New York City that would be a subway train. In Texas, an extended cab pickup truck. The answer is personal and depends on the person's life details. Married, single, kids, etc. Trading software is no different. You should think about what your trading would encompass and how you would enact it. Equities, options, crypto, day trades, swings, longer term, a single broker or multiple, technical or fundamental, feeds, etc. There are so many parameters to decide on. And as you get seat time and evolve, those assumptions change.
Once you have a general idea what you want to do you need to find a broker to execute your trades. Unfortunately in my case and many others, one broker may not fulfill all requirements. One broker can get you good fills but they never seem to be able to fill your short orders. Or you have a broker you like but their data feed is too slow or doesn't support Level 2 or in some way is not a fit for your trading. In this case you might need a third party data feed. Guaranteed that somehow your particular trading style is going to point out a resource problem.
Many brokers offer a free trading platform. I like free. I consider free. I try free. But free can cost you. In my opinion brokers offer free software to promote their business model, not yours. They're not mean and evil, they're a business. To me that means that there might be a conflict about what I want and what they want from my desire to take on risk and trade. Offering a free financial TV window means nothing to me since I already have a TV on the wall next to me. But it could be great if you're using a laptop while sunning on the beach. Brokers like to keep their customers so don't expect their software to interface to other brokers. You might end up with software from three different brokers plus a feed. Good luck trying to piece together a picture and placing trades as you constantly switch windows. Also expect one of those platforms to crash and take down your whole PC just as you click the sell button. And imagine the amount of time, and stress, after restart to get all the software up and running again. And it won't be "my PC crashed and I made even more money". The market knows when you're screwed. If a broker decides to discontinue a platform and replace it with something else, throw out all your customization, code, experience and prepare for a new learning curve.
I wrote more than I expected but I hope you get the decision making process. For me I realized I needed a third party trading platform to integrate all my brokers and feeds into one efficient app. Worrying about spending a few hundred bucks for it is silly since I could easily make that much on a single trade quickly executed. I decided that the PC, not me, should spend its time scanning the market for opportunities based on my algorithmic criteria, so I needed software that I could write scanning code for. When writing code you will invariably write something that doesn't work and when you contact tech support you don't want to hear "why would you want to do that?", or "we'll tell our tech people", and then never hear back.
I don't want to mention the platforms I've tried and rejected since they might be a perfect fit for someone else. Currently I'm using Medved Trader. I'm amazed at the number of brokers and feeds they support. They combine all the feeds into one program. For me I can be looking at a chart with a feed from one broker while I place a trade with a different broker while looking at news from another broker. I love the flexibility. And I can link to Excel to try out a new trading idea I have. So form a picture of what you want to do, check out the platform I mentioned plus others like the list on ET and see what works. Keep an open mind, one small feature could make or break your plan.
Share what you have tried and what you have decided to use!