Yes, Lore's Borg were scarier & more dangerous than the regular collective in my opinion, but not for the reasons you suggest
They were more dangerous, because they were rogue, & out of control, which made it easy for them to be manipulated by a strong mind like Lore. It's like they were the most hazardous WMD ever, & were ripe for the taking.
Frankly had it not been for Data getting control of himself, I could foresee a horrid future for the galaxy, wherein Lore, with the aid of Data, take over the Borg collective & conquer the whole damn galaxy, which was the REAL reason Lore wanted Data at his side. Data would be the only one who could stand in his way
Make no bones about it. Taking over that rogue Borg cube was not only the most fortuitous happenstance Lore had ever encountered, it was certainly his goal to use it as a launching pad to conquer the galaxy, in Hitleresque fashion
It's scarier simply because the Borg collective is an ominous unknown, but Lore is an all to well established evil, who's goal, ever since the days of the Crystalline Entity, was to decimate the Human race