The need for a big battery comes from several potential issues:

Do you ride in cold weather.  A larger capacity battery is needed if you are going to start the bike when it is cold (battery performance is down, oil is thick, etc).

Do you make lots of stops/starts when you ride?  The charging system is not very robust and it takes a while to recharge the battery after a start.  (A few members have run their battery down when they make lots of short trips).

Does your bike start quickly?  A bike that has to crank for a while can run the battery down and a longer ride will be needed to recharge it.

And finally and maybe most important - you need enough cold cranking amps to keep the battery voltage high enough to run the ignition system.  If too much of the battery power is going to the starter and the voltage drops - you won't get any spark and the bike won't start.

Although Lithium batteries are expensive and have their own set of issues - they are small and lightweight and able to provide full voltage to start the bike (when they are not cold).  If you are after small and light....they are able to provide that.  Lithium  batteries are ruined if you let them run down completely - a lot of the better brands have a safety built in that won't let you run them down low enough to be damaged...they disconnect when the voltage gets low.

If you want a Lithium - I suggest you not go too cheap and buy one that is a trusted brand and has some safety features built in.

Lithium batteries can be damaged/ruined if you let them go completely flat.  The Lithium batteries hold onto a charge for a very long time - but if you have accessories that you forget to turn off - or your bike has parasitic devices (computer, clock, unlocking devices, keyless ignition) the bike could run your battery down as it is parked for extended periods.  Be sure to turn everything off when you park the bike at the end of the ride, and although tenders are not generally needed for Lithium batteries - you may want to disconnect the battery or use a tender if the bike is going to sit for a while.  (My bike does not have anything drawing current when the key is turned off - it has sat for 5 months over the winter and fires right up in the spring.....it is been doing that since 2012 with the same EarthX battery).

You want a Lithium battery that is protected from Over or Under charging, you want one that has internal cell balancing, and you want one that will protect itself if you create a situation that will run all the power out of it (leave something connected or leave the key on).

AntiGravity and EarthX batteries are good choices.