A mailing from a messenger account is for a cold base: messages go out by phone number even to people who have never talked to you. It is flexible, but messengers treat such mailings more strictly — the pace and the text have to be kept under control.
A bot is the opposite: a channel for your own warm audience. It sends messages through the official Bot API only to those who started a dialogue with it themselves, so blocking is practically ruled out: no account warm-up, no speed limits and no caution with the text. The ideal scenario is regular mailings to your customer base: news, promotions, content, notifications.
Both formats work in one account and complement each other: find new customers with a mailing from a Telegram account, then turn the collected base into bot subscribers and work with it without restrictions.