I don’t know why debug would be that much slower. Offhand I can’t think of anything that would be so different in the MyEclipse for Spring product that would impact the performance of debugging. The eclipse environments are physically different installs so I’d look for differences between the two working environments like memory settings and maybe the number of breakpoints set.
I’ve heard of people having extreme slowness if they have many breakpoints in their breakpoints list, especially ones that correspond to code that has moved, or breakpoints set at the method level. You could try clearing all breakpoints from the IDE to see if that helps (assuming of course that you haven’t already done that).