One big difference between your 530S and some of the recent models is the mount. Your EasyPort is a lot more user friendly than the ones used on the Via and GO models in the 15XX numbers. The suction device stays WITH those, so if you take your unit in and out a lot, you'll miss the EasyPort. OTOH, the GO25XX models use a simple magnetic mounting that is easy to pull off and return to position.
Your 530S uses a resistive screen. If you are accustomed to poking at it with anything but your finger, you will quickly discover that while the 25XX has a much brighter display, your finger is required on these capacitive screen devices.
Any of the new models use a different connector for power than your 530S.
NONE of the newer models handles more than 3 or 4 waypoints/itinerary points. If you needed that feature, hang onto that 530.
You'll lose your compass page on any of the newer models.
There are lots of differences. It would help to know what features you depend upon now and what might be of interest. For example, a Live version provides Google search, fuel prices, weather and other stuff.
If you can live with the mount, the GO1535 Live is pretty nice. If you need the easier-to-use mount, the 25XX models are the way to go. If you've always wanted automatic on/off operation, the 2535 has that now.