On balance running with my dogs (at a Parkrun its either Seela the husky, who is nearly 12, or Beans the Springer (4) as you can run with only one) is about neutral in terms of time. Time gained by being towed is cancelled out by time spent drinking from puddles, cattle troughs and other doggy functions.
At Montacute's 1st anniversary Parkrun there was Liz and Martin Yelling. Montactue is a 'proper' park run, two laps around a large field. Martin blew passed most of the runners and finished in about 23 minutes pushing a double buggy with twins.
Canix is OK, I've done the Neolithic 1/2 marathon but most of the events are 5k and the idea of driving for 1-2 hours to get to an event that is over in 30 minutes does not appeal.
I've been ill this year, first of all with diabetes which resulted in cataracts so I went totally blind. Fortunately I have had both eyes operated on to remove the cataracts. The diabetes is now under control with twice daily injections of insulin, so I have re-started running. I've done 2 park runs recently and got my time down from 30:30 to 29:46. I think the second time would have been faster but we stopped to help an injured runner until a marshal arrived.
While I was ill Beans, a rescue Springer spaniel, joined us he is about 3 or so (actual age unknown) and completely bonkers. His best time for a parkrun is 26:20.
I'm getting on a bit, since I will be 11 next spring, but Bean and I, plus the two-legs are training to do the 20km route at the Stonehenge Stomp at the end of January.
The downside of Canix races is that they are all over the country and usually only 5k. (the major exception being the 1/2 marathon on the Neolithic trail). They are usually fairly pricey too, and expect you to have all the 'right' gear, which naturally they sell.
The upside is they are well organised and have a good atmosphere.