I would like to say some things.
Lucas F-smash with the stick kills and is faster and it has longer range than Ness' bat. Lucas' stick is very deadly and better than Ness' bat.
I do find Ness' air game is much better, the bair is very useful in killing people. Lucas' air moves can hit you a lot and do lots of damage if they hit you, but has less priority I think and he doesn't have any kill moves in the air like Ness does except upair, which Ness also has as well.
Ness PK fire I find much more useful than Lucas PK Fire (Lucas PK fire can only kill at very high percentages), I keep abusing the same PK Fire to Fsmash and it totally dominates online team matches. Most people online keep falling for the same thing over again.
Just remember when you use Ness PK fire on anyone, especially when fighting agianst Lucas or Fox or Falco or some other reflect/absorb people. Only do so when they're in the middle of an attack or you think you can catch them off guard. It's harder to do some on fast characters like Fox/Falco/Wolf but with Lucas, if he fails to hit with an upsmash or downsmash you can PK Fire him then get a chance to do an Fsmash on him.
The yoyo, when they go up you can damage them even more with a quick PL Flash too since it sends them straight up, but in my experience the PK fire to F-smash is more reliable than yoyo to PK Flash. I haven't tried the up yoyo to PK Flash yet, but I have to try some time.
If you want to use Ness, learn to use ForwardA a lot (not too much otherwise it'd diminish in damage and knockback), it's Ness most standard move and it's very good. Lots of priority, it sends them up and you can do an up yoyo or PK Flash on them.