i think every beatles record is not so strong. in my opinion, many of the mccartney/lennon songs were probably not so well written due to their constraints in releasing a record every year. the quality of the arrangements did improve however. the time they stopped touring, which was around early 1966. i still think that paul mccartney's 'mccartney' and george harrison's 'wonderwall music' were the most experimental of any of their work. if you like the beatles, try emitt rhodes' first record titled 'emitt rhodes'(1970) and even his second 'mirror'.(1971) gerry rafferty also has an amazing record titled 'can i have my money back?" which was recorded in 1971'. if you really like the beatles, with a touch of syd barrett, check out osamu kitajama's record from 1970 titled 'justin heathcliff'. it is a very neat record, he tried to emulate the 'beatles sound' i think and succeeded in doing so on his justin heathcliff record.
their strongest record in terms of recording and songwriting ability can be credited to their 1966 record 'revolver'
this record is assumed to be their 'breakthrough' record, after rubber soul and sgt. pepper, for its experimental quality.