Some others are Aweber, Email Aces and GetResponse. I use
Aweber personally, but they're all pretty much the same
As for HTML vs Text - can't you do both? That's what MIME is
all about
: being able to send several versions of the same email
message encoded in different ways, and then it's up to the
receiving email client to choose the appropriate one to display.
Or, send a plain text email with a link to the web based HTML
newsletter, so your readers have to click the link to read the
HTML page.