Trump's excellent attorney's made this point......if the Senate votes to allow new witnesses......it will extend the proceedings for months...tying up the Senate during that time.
If this becomes the new standard....where the House can ship over impeachment without needing to call witnesses in the House....they will do this as a precedent......doing a quick impeachment, and then forcing the Senate to stop everything they do, to deal with witnesses the House should have called during the impeachment......
This, all by itself, is a reason above politics to not call new witnesses........
I say call witnesses. All witnesses. Biden, his coke head son, Bolton, BO, John Kerry, Hellary,all the Ukrainians involved, the principals from Burisma, and anybody else who has ever had a thing to do with this. Make it painful for everybody. Then they all will think twice before playing the game of 100% political impeachment.