I will not spend too much time on such a trivial issue. If you want to find out which is historically accurate, research it for yourselves. One site I found interesting was http://www.jehovahs-witness.net/watchtower/bible/92381/1/The-facts-on-crucifixion-stauros-and-the-torture-stake but there are other sources showing that the cross, adopted from previous cultures as the Romans often did, is historically accurate. The important thing to remember is that Christ died for our sins. It doesn't matter what he died on.
However, a second point JW's bring up is that wearing the object Jesus died is disrespectful to God. This shows a gross misunderstanding on their part. Displaying the cross in a church or wearing one doesn't mean you are being disrespectful to God. It is a sign of respect for what Jesus went through. It is worn or displayed to remember the horrific death that Christ died so we may be forgiven. His death is bittersweet because it was terrible that he had to go through it but it shows God's love for us. He wanted us to have the hope of salvation.
So proudly wear your cross. It sends a wonderful message. It says, I know what he went through, and I am grateful to be loved so much.
As always, I welcome all and any comments.