In tournament play, it seems to draw out my most powerful pokemon... In short: What you didn't want just to have a level disadvantage, but thought it would be a great idea to pull out my level 80 water type when you have a level 40 fire type? =^^=
What strategy are you using for level grinding, by the way? Do you go for the easy but lesser exp giving 'mons at a much lower level than the ones you're training, or do you go for the ones about the same level but end up running back into town a lot to restore/revive every few fights? I usually do the latter but sometimes I wonder if I should try the latter.
As I'm starting the game, you really have no choice but to level as you go, and stick near the Poke-centers. Rematches with other trainers, and the gym leaders was a good source of cash and XP, but annoyingly difficult in HG/SS.
In HeartGold, once I beat the Elite Four for the first time, they became a treasure trove of cash and XP. (Once my initial team had levelled enough to beat them without incurring major medical fees! What I will do is take my level one Whatevermon, shove the XP share on his little head, then take him to meet the elite four! (Making sure that two of my team have the luck Incense, and Amulet Coin, of course wouldn't wanna miss out on scoring $100,000! ) If you start at level one, the critter will grow to at least 20! Cycle them through again, and you'll almost be at level 40! Now I can take them for the real training at Mt. Silver. The Poke-Center is right in the middle of the tall grass, so healing from damage and status issues is not a problem. I'll put the Shell Bell on the trainee, just to prolong the agony, err, improve training duration! =^.^;
Finally, if you have an electric type, or something that is not susceptible to water, the Good Rod catches level 40 ANYTHING! At my Silver, the lake inside the cave, that will be either a Seaking worth 970 XP, or a Gyrados for 1200! Anyone for fried fish?