My choice would be to use the Google Maps app on your smartphone if you use one. Always freely updated and provides live alerts to delays and offers alternative routes.
However, if you really want a separate stand-alone unit, my choice would be Garmin. I was using their kit in the late 90s for precise naigation on board ships (there were reasons it had to be precise) and their kit was always reliable. They have been at it longer than Tom-Tom, i wish i'd had the money to develop the idea i had of a commercial sat-nav before Tom-Tom did but that's another story!
Yes, Garmin tend to be more expensive than Tom-Tom but for a stand-alone, they are the best IMHO. Try and negotiate free updates as i believe they are chargeable and with so much development going on the roads are always changing. I remember buying a brand-new sat-nav in 2008 and it was already outdated, not even a free first update to make it current included in the price. That said it was a run-out model but even so! It showed me driving through fields on roads i knew were already a year old at the time.