I use the Rumble 40 v3 and it has the same controls and effects loop, as the Rumble 100 if you are referring to the Bright, Contour and Vintage switches. The only difference is the 12" speaker and more headroom in a slightly larger casing weighing only about 4 more pounds.
Another thumbs up for the 100, it does everything I need. Sounds great, weighs nothing,the overdrive is ok( get a foot switch for it) and it can rattle my home about once a week- when the coast is clear!
The 40 v3 lacks the effects loop (send/return) the 100 and above have.
It does have the same EQ, Tone shapers (Bright, Contour, Vintage), and the foot switch jack in the back. The 15 and 25 are more limited in options.
Anderson: You are correct although I am not sure how you would use the effects loop.
I was given the option of upgrading to the Rumble 100 for $100.00.
I figured the additional headroom and 12" speaker were worth it as I will be playing small venue gigs such as churches etc…, eventually.
To me, the lower Gain and Master settings, along with the 12" speaker, do make a difference and I am happy with my decision.