both have there merits, both are great. both have great utilities. and modulators, etc.
toybox is perhaps more accessible, in making different kind of modular systems, but for experts there is also enough. it has samplers and a wavetable module, or even 2?
euroreakt you can use in ensemble mode, or the build mode, it is still available as a user library, but as an ensemble.
look at the modules they give, decide on what modules you like most.
i opted for toybox, because i have already more soft modulars, even one with some hetrick modules. and euro reakt is still there on my hardr drive, with 2 other great user block placks. and i do mind patching in build mode.
in the end i will buy the euroreakt rack blocks, once my budget is under control again...
you can't go wrong, in both you can play endlessly. but look at the sites, the modules included, and you get an impression what they can.