I too am going to use Allflex bubblegum (small loop) for my small eared Shetlands. They had good reviews on retention rates, altho there do seem to be probs (with these and prob other tags) if they are tagged when the ears are small and then the ear grows and the prong depth between the strips isnt enough and the ear gets infected.
For that reason and cos they always lose some and at £1 a shot that aint cheap, Im not tagging until nearly the 9 month deadline for outdoor kepts sheep in Scotland. Mad, eh, EID has meant my young sheep go without any ID for longer than they did previously!
In Scotland (dont know about rest of UK), the EID tag is yellow and the non EID one you can choose a colour, mine are pink!
Some will go for meat but as Shetlands normally dont go until their second year (not much on em otherwise, and I prefer them to have a decent lifespan for frolicing), all of mine will be double tagged as routine.