Classic Telegram software installs on Windows and works for exactly as long as the computer is on. The machine sleeps overnight and the campaign stops mid-way. You leave for the weekend and the warm-up never ran. You change laptops and you are moving sessions, proxies and settings by hand, while the send history stays on the old machine.
The second difference is the IP address. With a desktop program all traffic goes through your home connection by default unless you configure a proxy for every account manually. Here the proxy binding happens when accounts are uploaded and is visible in the table: each account has its own address, and the load per proxy is a column of its own.
The third is process state. A desktop program usually shows the current run and forgets it once closed. In the dashboard a campaign is an object: it has a status, a pause, a schedule, daily caps, a line-by-line send log and an error breakdown per account. You can stop a campaign in the evening and resume it in the morning from the same point, then come back a week later to see which account produced the most errors and why.
The honest downside: a browser dashboard needs an internet connection and trust in someone else's server — your account sessions physically sit with us. If that trade-off is unacceptable to you, a desktop tool is the better fit, and that is a reasonable choice.