My 2c would be guidescope performance is more dependent on the stability of the OTA, guide optics and mountings. For 2 refractors, hopefully you won't have any issues with optics moving (as is possible in Newts and SCTs). That leaves the quality of rings and attachments as well as optical train for both refractors.
I guided using a WO ZenithStar 80mm piggybacked to my FSQ for 18 months with good quality (WO) rings and dovetails. Changed to OAG 9 months ago and stars are way better.
Prior to using the ZS80 I used a 50mm guidescope in good quality rings - can't really say there was any benefit with the longer FL - although it did look nicer
Your experience my differ from mine......