When comparing Reaper vs Seq24, the Slant community recommends Reaper for most people. In the question“What are the best DAWs?” Reaper is ranked 1st while Seq24 is ranked 49th. The most important reason people chose Reaper is:
Reaper lets users change to different themes, supports the use of a wealth of (free) extensions and has a lot of options when it comes to rendering.
Specs
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Pros
Pro Highly customizable
Reaper lets users change to different themes, supports the use of a wealth of (free) extensions and has a lot of options when it comes to rendering.
Pro Supports unlimited number of tracks with unlimited number of effects
There are no limits on amount of tracks and effects that those tracks can be equipped with.
Pro Rarely crashes
Most DAWs have a tendency to crash constantly, reaper crashes very rarely.
Pro Constantly updated
Alongside generally quick pace of updates, Reaper developers pay very close attention to user feedback and are constantly adding features based on their requests so much so that some even consider it somewhat of a crowdsourced DAW.

Pro Auto-bridges 32-bit plugins in a 64-bit environment
When using a 64-bit installation of Reaper, all 32-bit plugins will still work alongside 64-bit plugins. On computers with an x86-64 CPU and an OS that supports multi-architecture, you can also run bridged 64-bit plugins on 32-bit Reaper.
Pro Portable
Reaper is lightweight enough to be run off of a flash drive; the installer weights less than 20 MB and the portable installation option is included in it.
Pro Highly affordable
The Reaper DAW offers 2 licenses. A commercial license at $225 and a discounted one at $60. Both licenses give access to the complete DAW. The discounted license is for non profits, educational programs and personal use as long as yearly gross revenue does not exceed USD $20,000. There's even an indefinite free trial with no limitations for evaluation purposes.
Pro Very low cpu usage
Reaper's will tailor itself to fit your computer's processing power by automatically using the "anticipative FX processing" feature.
Pro Multi-level freezing
A freeze can be applied to a group, and then picked apart track by track.
Pro Comes with ~300 free plugins
Pro Easy to install
No complex activation shenanigans. No dongle and such.
Pro Simplified workflow
In Reaper, a track is a track is a track. There is no distinction among MIDI, stereo, mono, surround or any other tracks, and that means it's possible to put clips of all kinds on the same track. This approach makes the Reaper DAW seem a lot more intuitive than other DAWs.
Pro Lua scripting can be done in the DAW with a built-in IDE
Pro Free Reaplugs VST/VSTi bundle allows usage of the basic bundled like EQ's and comp plugins in any DAW
Pro Huge community support
Pro Multiple recording and playback formats
Records in WAV, AIFF, FLAC, WAVPACK, OGG and MP3.

Pro Notation editor added recently
Pro Supports ReWire
Pro Tabbed projects
You can have open multiple projects via tabs at the top left and easily drag and drop clips, instruments and ideas between each project at ease.
Pro DRM-free
Essentially shareware. After your 60-day free trial runs out, the program does not enforce the end of the trial period, and you may continue using the software for further evaluation or non-revenue generating purposes indefinitely. The only "DRM" is your conscience, the Digital Millennium Copyright Act, and the fact the program is awesome.
Pro Application is extendable
The Application itself has no limitations. Once you understand it you can progress onto the better mastering and editing qualities then all other DAW applications.
Pro Editing audio can be done on track
You don't have to go to a separate editor to edit audio files. You can work directly on the track, and drop/drag pieces to other tracks, sew them together. It's a fun sandbox and easy peasy.
Pro Very full featured but basic recording and production can be learned and done in a few hours
Without prior experience with DAW, you can install Reaper, set up ASIO drivers, connect to your amp and mikes, get the hang of recording/re-recording tracks, and render an mp3 in just a few hours. You can accomplish the basics very fast.
Pro Runs well on Wine in Linux
Pro Many time-saving features
Thought has been given to many time-saving features and shortcuts which speed up workflow considerably.
Pro Tool-less interface
Set the cursor, press a key, done. No need to switch cursor editing modes or work around "smart" cursors.
Pro OSC-Support
You can control nearly everything via OSC (and Midi, too).
Pro Native Linux support
No need to install Wine, Reaper supports Linux natively!
Pro Clean, easy-to-read GUI
The GUI is simple and easily gets information across to the user
Pro The software advances with you
If you want to use it as a glorified tape machine and nothing else, you'll still be able to get work done. If you want to learn all the shortcuts, scripts, custom actions and macros and really unlock what Reaper can do, you can do that as well. Either way, you'll still be able to make music.
Pro Open source
Seq24 can be used and edited by anyone for free.
Cons
Con Long drop down menus
There are many features that you'll find nested deep in the menu system, but it's really clunky. Everything is there but it's difficult to find. It's also really easy to accidentally click an option that you didn't intend.
Con Lacks VSTis
Doesn't come with a wealth of VSTis. Plugins for things like piano, cello, guitar have to be found elsewhere. But is highly compatible with other providers of those products.
Con No native groove quantize feature
Straight quantization is available, but the Reaper 4 DAW is still missing groove integration. This feature can be made available with the free SWS extension.

Con No PFL metering
If you want to meter your input levels before your FX and volume fader, you'll need to insert a metering plugin as the first part of the chain, since there is no option for PFL metering.
Con Midi Latency is still an issue
Con Midi drum editing not so fast or easy
Cubase has more features for creating and editing midi drum tracks.
Con Horrible GUI
The producer or composer need a good feeling when they work with their DAW.
Con MIDI only
Seq24 only has MIDI capability, no audio clips allowed.
Con Low compatibility
Seq24 only runs on Linux and win32.