Jelco vs Rega

I have an Avid Diva II TT with the Jelco ST 250 arm. Would changing the arm to a Rega RB 301 be a worthwhile upgrade or would it just be a lateral move or worst yet, be a downgrade. Thanks.
I think the Jelco arm you have is as good as the RB301. The Rega is an excellent arm, but so is the Jelco.

If you want to upgrade arms, a SME 309 or a Moerch or maybe an older Graham 1.5 would be nice on that table.

I have a friend that has that same table with the new SME M-2 arm and he really likes it. I would spend the extra money and get the 309, if it were me.
... Or upgrade to a Jelco 750. Owner feedback I've seen on these indicates they approach the performance of an SME 309.

If I ever re-arm my Technics SL1210, it'll be some version of a Jelco 750, probably the S-arm w/detachable headshell because I'm so used to that. The straight arm/fixed headshell version is pretty much what the AQ PT-9 was, right?
I put an Origin Illustrious arm on my Avid TT and the results were really great. Ortofon, P Windfield Cart is outstanding with this set up also.
the jelco
Dear Rsfphil: The Jelco tonearm have to me an additional advantage due that it is a removable headshell design that permit ( changing different build/weight material hedashells. ) a better match between cartridge and the tonearm to have the " best " cartridge quality performance.

Regards and enjoy the music,
The ST250 doesn't have a removable headshell.
Dear Rsfphil: My mistake, I don't read the " ST " that is the one from Jelco that is non-removable headshell design against the SA-250 that comes with removable headshell.

Regards and enjoy the music,