As I've said before, I think that Connors was better than Lendl at the majors, and Lendl was better than Connors away from the majors. Their 'prime vs. prime' 1981-1984 h2h summarised that.
In my opinion Connors's haul of 8 major's is more impressive than's Lendl's.
The most important tournament for both players was the US Open (Lendl said many times in the early 80s his main career goal was to win the title there), and Connors won it 2 more times than Lendl, beating him in the 1982 and 1983 finals.
And Connors won the biggest tournament in tennis Wimbledon twice, while Lendl never won it at all. And we know how obsessed he became about trying to win it in the late 80s and early 90s.
The grand slams were less equal in the 70s and 80s than they are now, and Connors's 7 Wimbledon/US Open titles compared to Lendl's 3 is a big advantage.
Lendl never won a major on grass and never won a set in any of his 3 major finals on the surface. However Connors won the 1976 US Open title on clay, thumping Vilas in his semi-final before beating Borg in the final. He has victories in major finals over Borg on clay, McEnroe on grass and Lendl on hard courts, which is a big feather in his cap.
Connors's 1974 Australian Open title is very lightweight. Then again Lendl was very lucky to win his 1990 Australian Open title, with a clearly injured Edberg serving for a 2 sets to love lead in the final, before retiring in the 3rd set (he had played flawlessly in his SF demolition of Wilander).
Lendl's non-major record is certainly more impressive than Connors's. Quality over quantity his official 94 title haul has always seemed more impressive to me than Connors's 109, as Connors has a lot more weak, lightweight title wins on his record, and Lendl has a better balance/distribution of good quality title wins across both Europe and North America. And Lendl's record in unsanctioned events (which were very lucrative and highly regarded) was absolutely unrivalled. Overall he actually won more titles than Connors. And of course he won the year end Masters 5 times.
Plus Lendl led Czechoslovakia to the 1980 Davis Cup title, while Connors is the only open era great that has not played a major role in winning the competition with his country. He only played in 8 live singles rubbers during his career, and his big defeats against Ramirez in 1975 and Wilander in 1984 are more notable than any of his 6 victories. Every other open era great played in at least 20.