I've been to both.
LPN schools are just as challenging, but in a different way. The biggest difference is time, and ultimately, money and opportunities.
The LPN programs fit in didactic and clinicals in 1 yr, ADN/BSN fit those components into 2 yrs. So, you learn alot MORE, over a longer period of TIME in an RN program.
And that translates to a difference in pay and opportunities. LPN/LVNs make, on average, 5 dollars an hour LESS than RNs. And, with hospitals trending to RN staffing, there is a shortage of RNs that equates to more finanical pressures to increase RN salaries over LPN. (Because less LPNs are being hired into hospitals, there is a relative less supply then demand for those positions.)
In the past 3 yrs, I've seen huge 'market re-adjustment' raises for RNs that were not given to the LPNs (or rather, not in as large an amount.)
For example, the last such 're-adjustment', RNs were given a 10% raise, LVNs, 3%.