These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
W, in general, is by far the most popular of the Nintendo DS SRWs, and was the most popular handheld SRW until Z2 came along, with some having gone so far as to consider it the best SRW period when it was released. Literally the only real complaint was that it could be a bit easy compared to previous titles, and that's mostly due to certain units or unit groups being surprisingly easy to "break" simply through competent, average play.note The GaoGaiGar units and Ardygun family units being the biggest offenders in this regard.
Expy: The 'Val' series of mechs are a clear nod to the SRX team. To whit:
Goddamned Bats: The Radam Tekkamen are not only durable, but have high mobility and offensive weapons. Later, these units gain a second HP bar using units similar to Tekkaman Blade's Pegas. This also applies to the Eyds. However, due to the amount of GameBreakers and W being mostly an easy title, these units are considering annoying rather than actual threats anytime they appear.
While these bossess with their "Lambda Drive"-equipped units are deadly later in the late, they fail to keep up with the incoming GameBreakers received. As dangerous as a Gauron is by being able to take two actions during an enemy turn, use Spirit Commands and weapons fueled by the Lambda Drive, he still can't keep up with a heavily upgraded "Valguard".
Ankoku Daishogun, provided you want to gain a Secret Character: not only does he bring multiple sturdy mooks, each with Standard Status Effect weaponry to fight you, he's extremely resilient and powerful. To make matters worse, you cannot use Big Volfogg for this stage (only normal Volfogg). This poses a challenge for a player doing a "No Upgrade Run" where the only way to destroy him in five turns is to fully abuse combining mechanics of the The Ryu robots.