Spektr-R and IBEX are both dancing with the Moon. They are both in high Earth orbits that are strongly affected by perturbations from the Moon and possibly the Sun. According to Wikipedia:
In June 2011 IBEX shifted to a new orbit that raised its perigee to more than 30,000 kilometres (19,000 mi). The new orbit avoids taking the spacecraft too close to the Moon, whose gravity can negatively affect IBEX's orbit. Now the spacecraft uses less fuel to maintain a stable orbit, increasing its useful lifespan to more than 40 years.
You can see by the plots below that both Spektr-R and IBEX have semi-major axes that vary between about 170,000 and 200,000 kilometers. But while IBEX's eccentricity varies between about 0.4 and 0.65, Spektr-R's eccentricity varies betwen about 0.6 and 0.95! Recently it seems to be the case that IBEX reaches a higher apoapsis than Spektr-R, and IBEX has historically had the higher semi-major axis and longer period of the two. Recently however (2016), Spektr-R's semi-major axis has spiked from about 170,000 to 200,000.
Due to a reduction in TLEs for both spacecraft starting in 2017, it's going to be a difficult job to say which is in the "higher" orbit definitively in the future.
Orbital parameters deduced from TLE dumps: