The 595 seems to have a couple of quirks that were carried over to the XT. Odd behaviour that the 590 does not have.
But if you like the Live Track and the Edit Route / skip facilities ... the 595 is a pretty safe bet.
The XT. I ride with it all of the time, but I am on roads with which I have a broad familiarity. I know a lot about it, but if I deviate from a route, I simply cannot trust it to navigate me to the next route point without me running out of fuel before I get there. This would be disastrous in a place that I do not know. I'll illustrate that point with an example from yesterday when I get my XT screen shots onto my PC.
On the other hand, the combination of a route and a track do work pretty well on the XT. But that facility also exists on the 590 and 595.
Example of Unexplained behaviour on the XT.
The first image shows the route that I plotted in magenta. Underlying thatit the track of the route the roads that I followed in dark blue. The route started about 20 miles to the right. The first Via Point flag is shown on the screen shot. (Near Harewood if you know the area). The seconf route point is a Shaping point. This is placed just south of Tadcaster at a village called Towton.
Although I deviated from the original route, I passed through both route points. After Towton, the stanav was happy to route me ahead, but it wanted to take me onto the A1. This part of the A1 is a two lane motorway and is invaribaly brought to a standstill when one lorry doing 59.1 mph tries to overtak another doing 59mph. I prefer to avoid it, so I head East onto the A19 heading south as shown by the blue track.
For the rest of the journey, the satnav is trying to take me back to the motorway. Before running this route, I checked on the XT how it would navigate me towards my destination starting from different places along the blue track. IN the middle of that track is a village called Hambleton. If I place my start point at the East end of that village, the XT will navigate me East and then South to the end point. If I place at the West end, it will head west to the A1 until can turn East direct to the end point.
I expected the stanav to re-route me in the direction that I was heading after I had passed through Hambleton. It didn't. It kept trying to get me to go back. I stopped and checked whether it thought that I had missed Towton. Towton was still in the skip list (oddly), but the Via point wasn't marked on the map any more, and the route made no attempt to visit it.
The second screen shot shows me two miles from my destination. I am the green flag. Destination is the chequered flag.
The route is still heading me back up north, back through Hambleton and then down the A1. Along the original route.
Stupid.
It isn't for me to advise, but I would not recommend the XT to anyone for serious navigation. It is good fun to play with, and it has a brilliant screen and a lot of very usable features. Navigation from route point to route point after encountering a closed road doesn't appear to me to be one of them. I like the 595 and have mine set up as a 595 for the majority of the time. If I am going to places new to me - I'll have the XT on the dash where the pillion can see our progress, but the 595 is positioned between the bars as a faithful standby.
And if you don't like the 595 and want the ultra-reliability of the 590, then its a 5 minute job to switch the software. (I've only done it to and from an original 590 though). I quite like it as a 595 though. I think the software that I acquired is a USA version as it does not switch to portrait mode ... not that I want to.