I was talking to Lucas Mainers in general in an attempt to head off the usual "lulz, we has projectile, we wins we pwnz you noobs".
I believe Lucas could have a Dtilt lock on Ike due to it's speed. Pull off maybe 15% at lower %s? I wouldn't know the exact number, but I believe it's fast enough to rack up some damage.
There is that Air-release Fair (I believe it was on Lucas, right?) to consider as well.
Lucas has a fairly good set of tricks to recover with. Zap Jump, PSI Magnet Pull, his good jumps, and PKT2. I believe he can airdodge during the Zap Jump which would making him harder to gimp. Between all of those, except for extreme vertical heights, there isn't a lot of places he can't recover from. Combined with the fact he's fairly heavy (at least to what you would expect), he can be fairly difficult to KO if the move doesn't right out kill Lucas.
His Up Smash is the second strongest Up Smash KOing wise, with only Ivy beating it. As it, it's strong then our Up Smash. Thankfully, if he misses, there is a LOT of lag. I believe possibly more then the lag Ike has after his Up Smash. And it has less range. I believe he can Hyphen Smash it fairly well, so watch out for it. Fsmash is strong, but not as strong as Ness's (IIRC), and can reflect projectiles, so keep that in mind if playing at Green Greens or Distant Planet.
While he has a nice air game, it's not as good as Ness's, and his spikes are less powerful.
I honestly think Ness would be the harder of the two but this is the Lucas match-up. And we need smart Lucas Mainers over here...
EDIT: THANK GOODNESS. Last time I saw it, it was 7-3 Ness.