Hi Ben,
to IIS, mate.
They are two very different beasts, the greatest difference is their size, one a 10" aperture the other just 4". This difference is what is most significant, not the length of the tubes. Astronomy is all about collecting as much of the faint light as possible. A 10" scope collects more than 6 times the light of a 4". The image quality as a result is most significant, with the larger instrument being able to show much more detail.
I understand the size of a 10" solid tube Newtonian is considerable. Would you consider an 8" dob instead. Its size is much more manageable, but the aperture grunt is still 4 time that of a 4" scope. You WILL see a lot more in an 8" than a 4" too. You will see not only more detail in the planets with an 8" scope, but you will see detail in galaxies that you won't in a 4". An 8" scope is an extremely capable instrument. The dob I use most at home in Sydney is my 8", not my 17.5"! An 8" dob is no slouch.
A go-to function is nice, but not necessary. There a plenty of smart phone apps that can be used as finder charts with amazing detail. Many people use their smart phones for this very purpose. You can just punch in the object you are interested in, and the phone will show you where it is in the sky in real time. You can also point the phone in any direction of the sky, and it will show you what can be seen in any direction, moving the image as you move the phone. Some people are even mounting their smart phones onto their scopes, using them as a push-to function to locate the objects.
I would strongly suggest you consider an 8" dob over a 4", regardless of the go-to function the 4" you mention has, if a 10" is too big. You will end up disappointed with the image given by a 4" if you've already used a large dob.
Mental.
