Much of Stalin's willingness to purge stemmed from a unreasoning paranoia that made him horrendously suspicious even of his closest supporters. Lenin didn't suffer from this... he could be paranoid, but not unreasoningly so like Stalin could. So by default, Lenin's gonna be less willing to purge because he lacks some of the personal impulses that drove Stalin to be so willing to purge. Of course, "less willing to purge" is not the same as "unwilling to purge" and undoubtedly there would still be purges, but they wouldn't be as harsh or widespread as under Stalin.
Stalin seems to have reasoned pretty well*.
(*Well for a fanatic with some notably bad starting assumptions, that is.)
Also, I suspect that the Bolshevik regime itself was paranoid. They're always looking for the next Capitalist threat, they're in a situation where losing control could happen quickly and be utterly catastrophic, they're surrounded by people who really do hate them, they have an over-powerful secret police feeding them concerning information and many of the decision makers have been part of an illegal political organization that spent most of its existence at that point being hunted by the Tsarist regime (and very successfully at that, would-be revolutionaries could never be sure who among them was an informant). Add on top of that Stalin giving himself such a large degree of power that I suspect power itself may have been a major part of what drove him mad.
And I suspect that the regime under Lenin wouldn't look too different, so even if Lenin doesn't go crazy from power, he's still got a paranoid regime feeding him the information he needs to logic himself into being paranoid.
Also, paranoia wasn't the only reason for purges - Stalin also seems to have purged in order to engineer society. Now here, Lenin may be very different, for example, he and Stalin had different outlooks on nationalities within the union - so maybe under Lenin the USSR avoids the Stalinist force population movements. Lenin may also come to a different conclusion about how to deal with the rising bureaucrat class.
Long story short, I think there is a very large chance that Lenin could be as bad as Stalin.
While Lenin certainly wouldn't be much more upset by the deaths that would occur under collectivization then Stalin, the reason millions died instead of hundreds of thousands had nothing to do with collectivizing during a "good year" or a "bad year" (that merely determined whether anyone died to begin with) and everything to do with Stalin's active malice in refusing to release food aid despite the fact it would have had no impact on the overall program. I find it hard to see that Lenin would be so needlessly murderous. He could be murderous, yes, that is not something I've claimed otherwise, but not pointlessly so like Stalin was.
I think that even if the rains had been more cooperative during collectivization, the violence used by the state would still mean hundreds of thousands of deaths.
And I really wonder if Stalin could have distributed food aid even if he had pushed for it in a timely fashion - the food distribution network was run by NEPmen who he'd just killed or sent to the Gulag... (Just to note, this would still the fault of Stalin and the bolsheviks, just in case people misread this as a defense of the man.)
fasquardon