The TX model is out of live according to Netgear. What is the -100EUS model old new or what

The TXM has, among other things, 2x SFP+ instead of only 1x like the TX, but 8x RJ45 with generally higher bandwidths. The backplane also has almost twice as much throughput with 140GB/s compared to 78GB/s. It supports twice as many MAC addresses and also has a larger packet buffer.
In general, it is the larger model, which also justifies the price difference if you need these improved functions.

2 SFP+ ports on the MS510TXM, compared to one on the other