Pros of aria2

• Supports a wider range of protocols (HTTP, HTTPS, FTP, SFTP, BitTorrent, and Metalink)
• Offers more advanced features like RPC interface and multi-source downloads
• Has a larger and more active community, with frequent updates

Cons of aria2

• More complex to set up and use compared to Axel's simpler interface
• Requires more system resources due to its extensive feature set

Code Comparison

Axel (simple usage):

axel -n 4 http://example.com/file.zip

aria2 (equivalent usage):

aria2c -x 4 http://example.com/file.zip

Both tools support multi-threaded downloads, but aria2 offers more advanced options:

aria2c --max-connection-per-server=4 --min-split-size=1M http://example.com/file.zip

This command sets the maximum connections per server and minimum split size for segmented downloading, demonstrating aria2's more granular control over the download process.

Pros of curl

• Versatile tool supporting multiple protocols (HTTP, FTP, SMTP, etc.)
• Extensive documentation and wide community support
• Cross-platform compatibility (Windows, macOS, Linux)

Cons of curl

• Slower download speeds compared to Axel for large files
• Lacks built-in download resumption and multi-connection support
• More complex syntax for basic download tasks

Code Comparison

Axel:

axel -n 4 https://example.com/largefile.zip

curl:

curl -O https://example.com/largefile.zip

Axel uses multiple connections by default, while curl requires additional parameters for similar functionality:

curl -O https://example.com/largefile.zip -r 0-1023 -o largefile.zip.part1 &
curl -O https://example.com/largefile.zip -r 1024-2047 -o largefile.zip.part2 &

Axel is designed specifically for accelerating downloads, making it simpler for this task. curl, while more versatile, requires more complex commands to achieve similar download acceleration. However, curl's broader protocol support and extensive features make it a more comprehensive tool for various network operations beyond just downloading files.

Pros of Transmission

• Full-featured BitTorrent client with a GUI, web interface, and daemon
• Supports more advanced features like RSS feeds, watch directories, and encryption
• Cross-platform support for Windows, macOS, Linux, and more

Cons of Transmission

• Larger codebase and more complex to set up compared to Axel
• May be overkill for simple direct downloads
• Primarily focused on BitTorrent, less optimized for HTTP/FTP downloads

Code Comparison

Axel (HTTP download):

while((size = read(fd, buffer, BUFSIZE)) > 0)
{
    if( (i = write(outfd, buffer, size)) < 0 )
    {
        return( 0 );
    }
    *bytes_done += i;
}

Transmission (BitTorrent download):

while ((piece = tr_peerMgrGetNextPiece(tor, peer)))
{
    tr_peerMsgsRequestPiece(msgs, piece);
    n_pieces_requested++;
    if (n_pieces_requested >= MAX_CONCURRENT_REQUESTS)
        break;
}

The code snippets show that Axel focuses on simple HTTP downloads, while Transmission handles more complex BitTorrent piece management.

Pros of qBittorrent

• Full-featured BitTorrent client with a graphical user interface
• Supports magnet links and torrent files
• Includes built-in search engine for torrents

Cons of qBittorrent

• Larger and more complex codebase
• Requires more system resources
• Not focused on direct HTTP/FTP downloads

Code Comparison

qBittorrent (C++):

void TorrentHandle::addTrackers(const QVector<TrackerEntry> &trackers)
{
    if (trackers.isEmpty()) return;

    const libtorrent::torrent_handle nativeHandle = m_nativeHandle;
    for (const TrackerEntry &tracker : trackers)
        nativeHandle.add_tracker(tracker.nativeEntry());
}

Axel (C):

void add_url(char *url)
{
    conn_t *conn;
    conn = malloc(sizeof(conn_t));
    memset(conn, 0, sizeof(conn_t));
    conn->conf = conf;
    conn->url = url;
    list_add(&conn->list, &conf->conn_list);
}

The code snippets demonstrate the different focus of each project. qBittorrent deals with torrent-specific functionality, while Axel handles direct URL downloads. qBittorrent uses C++ with object-oriented design, whereas Axel uses C with a more procedural approach.

Pros of Deluge

• Full-featured BitTorrent client with a robust GUI and web interface
• Supports plugins for extended functionality
• Cross-platform compatibility (Windows, macOS, Linux)

Cons of Deluge

• More complex setup and configuration compared to Axel
• Larger resource footprint due to its comprehensive feature set
• Primarily focused on BitTorrent, less versatile for general downloads

Code Comparison

Axel (C):

void add_url(char *url)
{
    conn_t *conn;
    conn = malloc(sizeof(conn_t));
    memset(conn, 0, sizeof(conn_t));
    conn->conf = conf;
    conn->url = url;
    list_add(&conn->list, &conf->conn_list);
}

Deluge (Python):

def add_torrent_url(self, url, options=None, headers=None):
    """Add a torrent from a URL."""
    if not options:
        options = {}
    if not headers:
        headers = {}
    return self.core.add_torrent_url(url, options, headers)

While both projects handle downloads, Axel is a lightweight command-line download accelerator written in C, focusing on HTTP/FTP downloads. Deluge is a feature-rich BitTorrent client written in Python, offering a GUI and extensive torrent management capabilities. Axel is more suitable for simple, direct downloads, while Deluge excels in BitTorrent-based file sharing and management.

Pros of yt-dlp

• Specialized for video downloading from various platforms
• Supports a wide range of websites and formats
• Actively maintained with frequent updates

Cons of yt-dlp

• More complex to use for general file downloads
• Larger codebase and dependencies
• Slower for simple HTTP downloads

Code Comparison

yt-dlp (Python):

ydl_opts = {'format': 'bestaudio/best'}
with yt_dlp.YoutubeDL(ydl_opts) as ydl:
    ydl.download(['https://www.youtube.com/watch?v=dQw4w9WgXcQ'])

axel (C):

axel_t *axel = axel_new(conf, argc, argv);
if (axel)
    axel_start(axel);
axel_delete(axel);

yt-dlp is designed specifically for video downloading from various platforms, offering extensive support for different websites and formats. It's actively maintained and frequently updated. However, it can be more complex to use for general file downloads and has a larger codebase with more dependencies. axel, on the other hand, is a lightweight download accelerator focused on HTTP/FTP protocols, making it faster and simpler for basic downloads but lacking the specialized features for video platforms that yt-dlp provides.