A choice that my friend made after deciding between these two options and his experience with the bike is great a satisfaction.
If you are stuck between choosing between the Thunder bird and Royal Enfield, I would suggest to go for Royal Enfield Bullet because the resale value is Good for bullet. In terms of looks Bullet is quite an obvious choice if you are a hunky guy especially. The rear suspension of thunder bird is better than bullet and you will have better experience for long journey on a thunder bird over the bullet.
Most of the cases whether be wheel base, disk, maximum speed, mileage etc. both are pretty much the same.