Why is iShowU Instant better than iShowU (v1 / HD / HD Pro)

Introduction

I recently had a customer ask "What's different in iShowU Instant, beyond iShowU v1?", requesting more information that is easily put into a comparison table, so I thought I'd write something with more depth.

First, let's talk similarities.

Similarities

1. Realtime: Both iShowU v1 and iShowU Instant (I'll refer to them as v1 and Instant from herein out...) are realtime recorders.  By that, I mean they record the screen, creating a movie at the same time, and after you stop recording the movie is immediately usable.
2. Audio: Both can record two tracks of audio, a microphone and the app/system audio. 
3. Presets: Both apps let you define your own presets.
4. User interface: Both apps have a simple to use interface.
5. Scaling: Both apps let you scale the size (width & height) of the recording.
6. Frame Rate: Both apps let you change the frame rate.
7. Timer: v1 has a timer, HD does not. Instant has both start & stop timers.
8. Watermarking: v1 doesn't have any watermarking. HD has limited support. Instant does it  :)

Instant contains a number of improvements. In this next section I've tried to list them as they relate to our previous products (v1/HD/HD Pro).  The section after that details features of the Instant that don't exist in v1/HD.

Differences & Improvements

1. Audio: While both apps can record app audio, Instant uses a smarter audio driver (called iShowU Audio Capture). If the app quits unexpectedly, the audio system won't be left in a messy state (this can happen with v1/HD).   Instant also handles volume change better. 
2. Audio Codecs: Instant also lets you record in AAC, PCM, Apple Lossless or IMA.  Instant lets you record > 2ch output. Everything from standard 2ch through to 8ch.
3. User Interface: Instant has two UIs. One is a basic mode that focuses on only the most essential options. The "advanced" mode (not to be confused with Advanced Features, which is an in-app add-on to Instant) tab contains all the options, and provides full control. You can switch between them at will, so if you want simple, you've got it. If you want more control / flexibility, you've got that too.
4. Scaling: iShowU (v1) lets you scale down.  Instant lets you do that and also force the output to a common size (e.g: 1280x720p). 
5. Frame Rate: Instant lets you change both the capture rate and encoding rate independently. This means it's really easy to create time-lapse movies with no additional processing (capture a 1 frame per minute, saving to a movie at 30fps).
6. Camera: v1 doesn't have the ability to capture the camera at the same time. Instant does, and you can choose to animate it being hidden, regular sized or full sized, all in realtime during recording.
7. Composition: Instant lets you capture keypresses and mouse clicks and provides more animation options.  In the case of Advanced Features you can change the position, size, font, border and fill properties of the keypress animation all from the realtime preview.
8. Realtime Preview: Instant provides a capture preview. If you want to see what your camera compositing, keypresses, animated mouse clicks and such will look like, you can do that in realtime without the need to do a "preview recording" to test it out.
9. Control Panel: Instant has a mini-window control panel that can be used to start/stop/pause recordings, without the main UI being shown. It's a little touch that can make for a less cluttered workspace on multiple display setups.
10. Timer: In Instant, you can choose to start recording after a duration, or at a specified time. You have the same options for stopping recording as well.
11. Watermarking: HD has some watermarking, v1 doesn't. Instant lets you place an image and/or text into the final movie. You can change position, scale, opacity, border and corner radius on these objects, as well as put in reflections and shadows if you wish.

Features that iShowU v1/iShowU HD doesn't have

In addition to the differences highlighted above, Instant has a number of features that iShowU v1 does not.  

1. Better retina support: You can choose to output retina sized movies from the output tab using a single checkbox.  
2. Selection: The ability to choose an app window just by hovering over it and clicking it.
3. Recording of iOS devices*: Record iOS devices directly into a movie
4. Background: Replace the recorded screens background with either colour, or some image. You can also hide icons or not.
5. Multi channel audio*: If you have a many channel input device, you can map where the channels are sent.  i.e: map input channel 5 -> left.  If you're creating a AAC 5.1ch output, you can map to the various centre, left back, left right (etc) channels as well.
6. Dynamics / Compressor & EQ*: Instant provides some audio units on the microphone pipeline, that you can use to enhance the mic audio (balance a mic or "cheap" USB headset, for example).
7. Flexible file naming: Instant has a token based file naming scheme, letting you name / collect your recordings as you see fit using tokens such as codec type, date, size, preset name and frame rate. There's even an option to produce continuous sequential recordings, even when older recordings are removed (so you can choose to fill gaps in your naming, or not, as you like).
8. Output Codec: Instant lets you choose JPEG, H264, ProRes 422 / 4444. 
9. Container type: Instant gives you the choice of  Quicktime of MP4 containers. 
10. Actions after recording: When done, you can choose to "do nothing", open with any app from your system that supports video (there's a dropdown list), enter editing mode*, or share the movie.
11. Editing*:  Instant provides some essential editing features including trim front/back, adding lines, shapes and text, and deleting sections.  The original media is left untouched, and a new "encoded" movie is produced as a result.  
12. Sharing to existing OSX services: You can share to any compatible service setup on your Mac, including Vimeo, Facebook, Droplr and so on (yes, YouTube is in there!).

* requires Advanced Features in-app purchase

I hope that helps!

Technically, Instant is a far more modern codebase.  iShowU Instant, and iShowU Studio 2 are SWB's primary products, now and in the future.