Just like with food, it is a matter of taste as to which is easier. To be sure the significantly smaller court and easier to hit ball make pickleball physically easier to play for more people at a wider range of ages and conditioning levels. Both sports can be played as either a one on one (singles) competition or a two on two (doubles) competition. Because the pickleball court is smaller, doubles is especially easy to play as it does not require nearly as much movement as tennis.
Tennis racquets are larger and longer than pickleball paddles and generate more power much easier. Both require some degree of eye to hand coordination but the shorter paddle is generally conceded to be easier to use sooner in the learning curve than a tennis racquet. This shorter paddle also allows quicker skill building for both forehand and backhand shots.
Both games require the use of a net, however, the pickleball net is lower across the entire court. Both use a right and left box as the targets for alternating serves.
The balls used in each sport significantly impact play. A tennis ball is hit with much greater velocity. Tennis serves have been clocked at over 160 mph at the highest level of professional player with the typical pro routinely hitting 120 mph serves. The pickleball moves at about one third the pace of a tennis ball. Outdoors, it is also more vulnerable to wind gusts because of its much lighter construction, hollow middle, and holes.