I have various leads/collars depending to fulfil the particular function I require.

Schutzhund requires that a dog is worked on a fur saver (large link choke/check chain)
Gundog work requires a rope slip lead

etc etc

So I choose the most appropriate collar/lead for the activity

I had to vote twice as mine are for function but they also need to be stylish. Obviously if your dogs collar is going to get caked in mud or soaked every day then you need something that's mainly functional. I just hate to see stunning dogs in tatty looking collars

I use different leads/collars for different dogs.
Kerrie has P@H flat lead, matching collar, and a long line (from Scallywags dog training/Sally Bradbury)
Poppy has a Flat Leather Collar, and a Flat Lead (same as Kez) also a show lead (which I bought and have never used!)
Rupert has an Ancol collar, a stop pull harness and a rope lead

Last two dont have long lines (they dont need em) Kerrie has hers for places where letting her off lead would be unsafe

ETA. I am anal about checking my dogs' equipment (on a daily basis) and I will only buy good quality equipment. I will not risk my dogs lives by buying poor quality/badly made equipment

I have a variety of collars.

Their everyday collars are practical and cost very little. Because the dogs are always in undergrowth, mud, water and everything else possible, their collars have a short life span. I choose something strong, something to blend in with their coats and in the case of the collies, something that doesnt break their fur.

I also have a set of collars for when they are at fun dog shows or I want them to look a bit more respectable. These are a bit posher, a bit pricier and stand out from the colour of their fur. I dont go for bling type collars or pretty colours. I go for a pattern that fits the dogs personality or breed so Flynn has a camoflauge one and one with embroidered pheasants on for example. A pink diamente collar just wouldnt suit Jessie's personality as she is a bit of a tomboy and can run with the big boys!

As for leads...None of them match, I prefer black leads anyway, and definately something that is practical.