I am going to take an admission in Master Program in UK university, but it require both so i am bit confused which one should i have to do, i want to prefer easiest one, can any one help?

First of all feel confident and do make your self comfortable with practice.
TOEFL is easier than IELTS
Why I said this is because in TOEFL you are on your own and you dont have to face a person to give them an idea of your ability so if you make a mistake their responce will not discourage you.
in IELTS the test has a phase where you have to speak or answer some question of another person standing infront of you.

Another difference is in scoring system. TOEFL score is like 250/300 with 5.0/6.0 in essay. and IELTS score is in 6 band or 7 band. In TOEFL if you score 250 you might get 7 in IELTS and if you score 200/300 you will get a 5 in IELTS. A score of 200 in TOEFL doesnt give a bad impression but the band info sometimes make it difficult. If you understand properly I mean is the levels of scoring is good in TOEFL as you have more intervals between each score while in IELTS if you loose some marks you might end up in lower band.

I prepared from barrons and gave a test in 2003. I did 10 test from Barron's edition and went through all of them to see what are my major drawbacks. It took me 2 weeks to do all of this. 1 hour for each test is nice timing and after 5 you will see that you can do 2 tests in 45 or less time. Do each test twice once on your own and 2nd time after you have checked it once (i did this with a gap of 7 days). I got 270/300 and 6.0/6.0 in TOEFL. Dont compare it with GRE Analytical Writing . TOEFL Essay is quite easy than GRE and it is not difficult to get good marks if you practice for a month.

There are lot of resorces for TOEFL speciallt yahoogroups just search on google and you will find all kind of softwares and ebooks to download and try before you go and buy some special books or CDs.

The rule of improving a language is consider yourself in a situation like in a bank, hospital, bus station and converse with some virtual officer,friend,shopkeeper and try to find words that you dont know and see them in a dictionary. A smart Synonym feature in Word can give you alternate words for the one you cant find a single word.

Hope this helps.