I have an Erg that I picked up on ebay years ago. I haven't used a regular Vasa pro since college, which is 30 or so years ago. From what I remember, the Pro is much more a strength workout than an endurance workout. I seem to remember that, as a distance swimmer, we would set the vasa to a low incline and try to do several minutes and it being very difficult. You can do more extended sets on the erg because of the damper settings. Also, it's more like actual swimming due to the alternating arms. Also, you get some metrics with the erg (pace, distance, stroke rate, etc.) I don't think you get any sort of metrics with the Pro. (Again, it's been a minute, so maybe that changed.) Is it going to make you better? I doubt it, at least not as much as actually getting to the pool. But, yes, it's probably better than doing nothing at all. There have been a couple of times where I went extended periods leading up to a race without getting in the water and I managed to do okay just using the erg, but I also have years of swim base in me.