I have 3 male dogs, a 5yr old working sheepdog, a 2yr old Welsh Collie and an 11mth old Border Collie. The two eldest dogs are not getting on very well any more. The 2yr old who used to be quite submisive has gained alot more confidence  over the last couple of months and I think is starting to challenge for leadership. Would I be better to get one or both neutered, if only one which one. I don't want the youngest neutered because I show him. They are all house dogs and I have no bitches.( there is an unspeyed bitch next door but she should be moving in the next couple of months.

There is no guarantee neuter will change anything its more often a behavioral issue that needs training . You could consider using superlorin and seeing if that makes any difference but may need to use on both dogs . That will last for around 6 months. hopefully others will have some helpful views for you too

I have a Border Collie, castrated for medical reasons.  I prefer to keep spayed bitches and entire males.

I second the use of superlorin, even if it means that you have to use on 2 males.

However, pastorals are my fav in the whole world, so you could send them all round my house!     

Think I'll give super wotsit a try for both of them, sorry JeanSW they won't be going any where.lol

As said, castration isn't a cure-all and the only guarantee is no unwanted litters.    Sadly if there is a 'situation' starting up between the 2 year old and the others, then you may have to think about rehoming him.   I had this with one of our boys who at around this time, decided he wanted to challenge his uncle.   I tried it all - including sticking them in our outside pen and telling them to get on with it (so I had the ability to use a hose if needed).   What did they do - lie nose to nose at the gate waiting for me to let them out again.    Only for it to all start up again later in the day, once indoors.   It was getting increasingly serious and with no sign of the instigator settling down at all, I had to home him.    His uncle was one of my two stud dogs and the youngster hadn't been used but he clearly had it in for his uncle.   I found him a super home, with two bitches of his own - co-owned him for a while until I knew it was all going to work out - went to see him after a few months to make sure and I then let his new owner have total ownership of him.   And the most important thing was peace returned to our small pack.

If you do go for castration, which would for me, be a pity because it may not solve the problem, always castrate the submissive one.   If the more domant one gets no 'answer', he'll have nothing to fight.