Yeah, I'd give it to the Notos.
The LRMs are long range, but even if the Summoner B had the ability to keep the fight there, it has a big issue. The Clan engineers, in their infinite wisdom, gave the Summoner B's primary weapon a limited ammo bay. Now, it's actually a pretty decent bay by Clan standards, but it's still shallow enough that if it's firing at the Notos at Long Range for most of the fight (Easily 10+ modifiers, given the speed of both), the Summoner may simply run out of LRM ammo before the Notos's armor is breached.
The Summoner's jump jets are nice, but though they make it harder to be hit, the cheesy MPLs + TC on the Notos offset it completely. The problem with JJs in this fight is it makes hitting LRMs with the summoner much more difficult, and the Summoner cannot afford to waste ammo on bad shots.
What's worse is that the Notos puts out more damage on average than it takes from the Summoner as soon as the Notos gets within firing range range (12 hexes and less). That is in addition to the Notos's (marginally) superior armor. Even with a range bracket advantage (ranges 9-12, 7-4), the Summoner has to maneuver magnificently to get better or equal to-hit numbers thanks to the MPL's targeting computers, and equal to-hit numbers for the Summoner is still a losing proposition at hexes 10-12
As the Summoner I want to be firing at numbers where I have decent to-hit numbers, but I also don't want to take more damage than I inflict. That means medium range on my LRMs at least, so the Goldilocks zone is hexes 13-14. That's... pretty dire. I'd much rather be the Notos in this fight.