I'm with KBIS and my excess is £160 and insured for 5k vets fees (7.5 for colic surgery) and some other bits and bobs. I therefore would not go for either as my vets recommend taking out policies of 5k vets fees.
£150 excess with £3k for vets bills (plus another £1k for vet recommended acupuncture or hydrotherapy, physiotherapy, laser treatment or remedial shoeing) and £1.25m liability for £23 PCM. (Plus the usual death or slaughter and theft or straying)
Unfortunately £3.5k doesn't go that far, my old horse had minor kick in the field - but right on his hock, it punchered the joint so he was rushed to horspital, emergancy GA while it was flushed, then he stayed there for a week on IV antibiotics then home and antibiotics and several vet vistis to change dressing the bill was £4k
100% full recovery and no complications or it could have been more.
I don't insure but if I did for the cost I'd want most eventualities covered and sadly it's not just colic surgery/ major investigations that needs more than £3.5k these days.