Is it better to build a pure deck or should you just go with mixed decks? Well the answer is like many other questions of this type, hard to determine.
I personally enjoy playing pure decks as in decks that carry all cards of the same archetype or play mostly upon a single synergistic pattern. I like seeing all the cards in my deck work together towards a single flavour and carry many of the same common characters. Furthermore, it’s generally easier to pilot and build around a close synergy since many of those types of decks play up to two colours at most.
Now are pure decks better than mixed decks? That’s quite hard to determine. Back in the day when card design was not as powerful as it is today with multiple different effects stacked on cards and overall weaker filter/hand advantage abilities, pure decks were usually considered to be at a disadvantage. Since pure decks try to work on a single strategy, they would find themselves lacking pieces in other colours.
Back years ago, colours usually dictated the effects by which cards would generally act or perform. Yellow would mean search effects and burst power. Red would mean salvage effects and removal. Blue was the colour for drawing effects and walling (opponent’s turn power). Green was for overall power and some search effects. Weiss Schwarz still carries some of these notions around, but they are far more loose comparatively to effects from years ago. For instance, red may still be the colour for salvage effects mainly, but its not uncommon to see a blue or yellow brainstorm also carry some sort of salvage effect now.
Honestly, nowadays I feel as if pure decks are about around equal power or slightly less powerful than mixed decks. With card quality going up, individual colours or even paired powers have many of the wanted card effects/abilities within them without forcing the player to tech into another colour. Mixed decks still have the advantage of running anything they’d like allowing players to pick between different combos or finishers as they’d wish without any restriction or synergistic clause holding them back.
I’d like to say that mixed decks carry an issue of multi-colour requirements in clock or level, but the vast majority of these decks are built in a way where multi-colour isn’t that big of a detriment or they run cards in a way where they don’t all have to be played at the same level. As for a performance comparison, that’s a hard feat to determine since deck building and deck building variants exist everywhere.
I personally find based on my own online experiences that true pure decks are usually much harder to come across (depending on the series). The closest to pure decks in tournament listings and results are usually mostly the same synergy but maybe up to four or even ten of different cards played just because of how strong or useful those cards’ abilities are. Not to mention, despite all the changes and upgrades over the years, not all archetypes or combinations have access to the commonly desired effects. For instance, my <Goddess> themed deck from Konosuba still does not have access to any runner of any kind if I were to wish to use such an effect.
Although, because of the fact that pure decks are locked to a specific synergy, they are sometimes able to access some pretty powerful cards that would normally not be available to the player if they weren’t carrying that exact synergy.
One of these examples is the card above. This counter lets you rest an opposing character which stops them from attacking entirely which is pretty big because it deletes a full instance of potential soul damage. This effect type will also stop any on-attack or combat effects from a card as well making it quite a pain to deal with. Although, this card only works if your whole field is carrying the <Animal> or <Plant> trait.
In conclusion to the question of pure or mixed decks? The answer is entirely up to you. Overall, I feel the widely accepted answer is that mixed decks are generally the most played and built because they open up all these effects and abilities that pure decks would not have access to. Before, consistency was the issue regarding mixed decks, but I don’t think that’s too much of an issue nowadays. As for tournament results I’ve seen, well the majority are for the most part, still mixed decks. I wouldn’t say its impossible for pure decks to win, but the stats still seem to show that they just aren’t in results.
Maybe you can prove me wrong? Maybe pure decks are the way to go, but people may be tied to the the allure of those strong cards outside their synergies? Who knows really? Let me know what you think.