You're definitely going to be able to build for cheaper and still get similar features - in fact, you can buy the DJI Naza boards (M or M-Lite) and get the same exact RTH and assisted flight modes. Where you'll run into an issue is with the risks associated with building your own. Mistakes can be costly. You run the risk of having to buy components multiple times because you could wire something wrong and burn up your ESC's or something. You also might have other unforeseen issues that cause you to crash in your first flight and then you'd need to buy new parts and rebuild. I guess I'll list some pros and cons, and hopefully some others can add to it, and that should hopefully help you make a decision.
Before I list those, let me answer your tx/rx question. What you bu there is really a matter of price vs. quality for the most part. You can get by with a lower priced tx/rx, but you may want to invest in something nicer like a Spektrum setup. I've run into issues with the Turnigy 9x when it comes to firmware and the quality of the gimbals that ended up costing me way more than a better transmitter. First of all, there was an issue that caused it to send at least half throttle to the rx when the tx turned on. This shot my copter into the ceiling of my house and cost me the following: over $100 in replacement parts (frame, motors, wiring, etc.); around $50 and half a day in paint and supplies to repair the ceiling, $30 for a smarty parts board to change the firmware out on the tx to er9x.... then I went ahead and got a frsky tx module and rx - which cost another $50 or so. In the end, the gimbals on the tx wore out very quickly and they don't (or didn't at the time) sell replacement gimbals for the 9x (only the 9xr) - so really, if I had bought a Spektrum 6 or 8 channel for $150-200, I would have been in better shape. Or if you go cheap, get the 9xr since they sell replacement gimbals for it - and get a frsky module and receiver. It's a little more than the 9x setup they sell, but you'll be in better shape. By the way, I've never had a problem with a Spektrum tx. Also, used Spektrum equipment has decent resale value.
Now - the pros and cons:
Phantom:
Pros
- ready to fly as soon as it hits your door step
- already tuned so you can start flying with confidence without worrying about "anything you might have done wrong" in the build
- big community of other phantom pilots, so tons of information if you need support
- tons of R&D behind the phantom, so great flight times, control, etc. etc.
- a decent amount of aftermarket development for modifications for the phantom
- if it's not for you, it's much easier to resell than a custom quad.
Cons
*depending on the context, these might not be cons.
- Cost - it's a great value, but if you're looking to stay on a tight budget and add and upgrade compontents (FPV, etc.) as you go, you may want to build yourself.
- Repairs - there is a huge community of people with phantoms as well as replacement parts available, but if you crash, you might not be confident with doing repairs yourself.
DIY:
Pros
- More flexible - you get to choose exactly what you build, whether it be a stable aerial filming platform or an acrobatic copter, etc.
- More rewarding - it's a lot more rewarding to build yourself and I'd say it makes it more addicting since you can build anything you imagine. Also, it probably makes you feel more a part of a community since it's so much more involved than just unboxing and flying a phantom.
- Easier Repairs - If you build a copter from scratch, you pretty much get enough expertise in every component to be able to quickly repair anything you may break in a crash or that burns up for one reason or another.
- Potentially less expensive - really, when you build yourself, the cost is up to you.
- Potentially Less Risk - so above, I said there is more risk, and that's true, but there is one area where the risk is less if you think about it this way: logically, you shouldn't add any FPV to start. You should build your copter and get used to flying it, tune it, etc. before you put expensive FPV equipment on it. So really, for less than half the price of the phantom, you can get a copter in the air to see if it's even for you - and also, if you crash, less money is falling out of the sky. I'll explain the more risk thing in the cons.
Cons
- Not as easy to get help - There are unlimited combinations of parts you can build with, so sometimes it's hard to find help on your exact issue when you have problems. Don't let this scare you though. Most components are very similar in the way they operate, so if you have an issue, you'll usually be able to find help that leads you to a resolution, but you'll need to understand enough to know what to ask about. If you have an issue with a phantom, you'll just say - hey, I'm having this issue with the phantom vision 2, or whatever and people know the setup. If you have issues with your own build, you'll have to list out the parts you're using and unless someone built the exact same copter, there might be more "recommendations" as opposed to exact resolutions. Although, you're usually going to have tx/rx and/or control board problems - so if you get a semi-popular tx/rx combo or control board, people can usually help.
- More Risk: So where there's more risk is in the fact that YOU might make mistakes and it could cost you. You could have a reverse polarity issue and blow up your ESC's, or you could not configure your tx/rx and/or board correctly and have your copter drop from the sky. In the end, these mistakes can really cost you. With the phantom, you're not going to have these issues. Although, again, I wouldn't let this scare you - it's way more of an adventure to build yourself, so if that's your thing, it's worth it.
Sorry if this is somewhat disorganized or if I said anything that doesn't make sense. I didn't proof read it.
