Quite a few had bigger casualty lists, and many were more specifically aimed at political targets rather than large numbers of public, but fair point that a bunch were very similar or worse-done.
Two points I would make about the comparison though, firstly the IRA campaign was very much one of fear more than one of death - deaths were an added bonus. Of course maybe that's the case in Boston as well, but it's too early to know right now. Secondly, the word used was "professional" - were the IRA professional? I guess in the context of terrorist attacks, that's probably not really a relevant term.
The IRA had structure, with ranks. They had a political wing. They had funding and training and available weapons. They had PR and issued coded warnings and press releases.
Compare that to the London Nail Bomber (who killed three, and maimed many more) (https://en.wikipedia.org/wiki/David_Copeland) who operated alone and got no funding from others.
Actually, the IRA typically issued warnings beforehand -- soon enough to evacuate, but too late to find the bomb. I've heard it described as a calculation to minimize civilian deaths that might stiffen British resolve.
