M&S at the London Olympics is worse then M&S at the Winter Olympics in almost every way.
Events
The events feel more like a test of patience then anything else. Oh yes, swinging the controller to right for the next half hour definitely sounds like fun, and having to do it for two rounds sounds like even more fun. The only event in Winter that took a significant amount of time was Curling, and at least that was fleshed out. Table Tennis is literally just swinging the controller to right and waiting for the CPU to purposefully screw up, and sometimes having to press the B button to perform your Special Shot when it's ready. Football's default time is 10 Minutes, and it doesn't use the special time speed up magic that was used in Speed Skating, you literally have to spend 10 minutes playing what is essentially a glorified minigame. It's almost exactly the same as Ice Hockey in Winter, which was only 60 seconds long.
Dream Events are the only developed events in London, and the fact that Winter just copy and pasted the exact same event onto a new map with items and was still just as developed as the Dream Events in London shows how undeveloped the main events in London are.. 90% of the standard Events are swinging the controller around like a madman (track events, swimming, table tennis, javelin, long jump, badminton), or to a specific rhythm (canoeing, gymnastic events, discus, hammer). Football (literally just Ice Hockey), Cycling, Equestrian, and Beach Volleyball are the only developed standard events in London. The only events I haven't mentioned are Fencing and Shooting, and while they require some effort, they're definitely not developed. In Winter a lot of the events gave you control over where you went, it made the events requires some effort, even if the CPU players were a literal joke. Bobsleigh and Skeleton required you to stay in the line, Snowboarding and Skiing gave you full control over what you did, and Speed Skating required you to turn. That may not sound like a lot until you remember that the Track events in London were just swinging the controller up and down with nothing else to them.
The amount of Dream Events is also lacking. Not every event got a Dream Event in London, while in Winter every category got an event, alongside the unique Dream Gliding and Dream Snowball Fight.
London Party
London Party is literally just the Party Games and Festival Mode rolled into one. It improves on Festival mode by having more then just Events, and improves on the Party Games by actually having depth. The problem? It's the only side mode. You can play events by themselves, or a mode that lasts 30 Minutes at the bare minimum. Want a quick series of events you can play with your friends in a short time span? Nope, you have to spend 30 minutes playing this mode. Want to play through a Marathon of events? Well you also have to play through minigames, collect stickers, and run around a map for the duration of the mode.
While London Party is an improvement over what came before it, it comes at the cost of variety.
Shopping
Shopping is purely worse in London. In Winter completing an event gives you a few Star Points, getting a medal gets you more, break an Olympic Record or World Record and that's even more Star Points, and completing a challenge for the first time gets you even more Star Points. On the other hand if you complete an event in London you get a Scratchcard, if you get first place, break a record, or complete a challenge well give yourself a pat on the back because otherwise you won't get anything at all. No matter how well you do you always get only one Scratchcard, no more, no less. Before you can redeem those Scratchcards for something you want though, you get to waste your time scratching them to get a chance at winning something that you don't want. Yes Mr. RNG, I really did want that Navy Blue Table Tennis Shirt instead of something cool like those remixes. The fact that I actively want to fail at winning anything should speak volumes as to how bad the concept of Scratchcards is.
Let's also talk about going to shops, because that's worse too. In Winter you had a nice little village for the menu. The shops were... shops, the village had the playable characters walking around it to give it some life, and you could even buy some decorations to make it look nicer. Meanwhile London is just a boring menu with no personality or anything interesting to it. You select whether you want to exchange the blank cards or scratch the new ones you've gained, then select what you want to buy on a menu and that's it. No village to look around and decorate, no hidden shops down an alleyway, just a boring menu. Even what you can buy is worse. In Winter you could buy Music, Cosmetics for your Mii, the Special Shop allowed you to buy special content such as previously mentioned decorations, the Winter Gear shop allowed you customise your Bobsleigh, Skis, Snowboard and Hang-glider, and the library allowed you to read about the history of the Olympics. London only allows you to buy Music, or cosmetics for your Mii, removing three things you could buy in the previous game.
The only real improvement is that you don't need a special item to change the music of an event, and you can permanently set the default music of an event, but everything else is pretty much a downgrade.
Overall I rate this game Sonic Heroes but with Guitars/10