Oh no! Not another, "learn me".. 
Learn me data acquisition. My goal is to find out where I'm wasting seconds at time trials, and use the system for racing later on. Predictive lap time is a must.
Is a sub $500 system like a Race Capture Pro good enough?
How many / which analog sensors do I want?
Do I need the ability to create custom composite "squiggly line" views of accel + TPS + brake etc, that I can review post-event?
What other features should I be looking for?
Will I be leaving some "learnings" on the table if I don't pony up for a more expensive system like a TraqMate?
Do I need video?
Car is OBD 1 Miata.
Without OBD II, there's not really any easy way to get data out of the car's systems.
Something like Harry's Lap Timer on an iOS or Android device will get you G based data and, depending on the device, correlated with GPS data from either onboard the device or an external GPS-- you could even use an iPod Touch if you pay for an external GPS.
If you already have a device with some GPS capability, all you really need is the app (starts at $9) and a mount for it. Even with an external GPS, you should be able to get close to all in for around $100.
The hard part with data acquisition is not the acquisition itself, these days that's about $100 worth of commodity hardware. The hard part is the analysis software, because a lot of it is slow, clunky, has a poor user interface, missing the sorts of features you'd want, etc.
As far as input channels go, IMHO if you're focusing on driver improvement then the useful ones are the accelerometers, GPS location (the higher the frequency of positions the better), RPM and then the driver inputs -- throttle position, steering angle, brake pressure. Possibly boost if it's a turbo car (because TPS and RPM don't give you a full picture of the torque). Unfortunately, your NA Miata isn't going to have either steering angle or brake pressure sensors from the factory, and if it's a 1.6 it doesn't even have a continuous TPS.
Yes, you want the "squiggly line" display so that you can review the data as a whole instead of having to view it in real time. Video by itself is useless except for posting videos to youtube. Video with a couple gauges rendered onto it is only marginally more useful. What you want is a "squiggly line" display in one window where you can click on any given point on the chart and it will display the frames from that point in another window.
I have a Race Technology DL1 data logger. The analysis software is powerful, but the UI is not terribly intuitive and it takes a lot of CPU horsepower to render the raw GPS+accelerometer data into an integrated speed/location track when importing the data. Running it on a fast, modern Macbook Pro (under vmware, no native Mac app, unfortunately) it'll suck down a 20 minute track session in a couple minutes. Trying to run it on my old Thinkpad (core 2 processor) would be 20+ minutes to import the same data. I don't have video integrated with mine.
In reply to Karacticus:
I want at least some analog inputs for TPS, steering angle, maybe brake pressure, temps etc. I don't think a phone app will do it.
