Almost the same, but only a little difference according to context.

i.e., we say "法定继承人" but not "法定承受人". "继承人" stresses on the right, while "承受人" on the result...

See following for more info.
legatee [ˌleɡəˈtiː]
n. 【律】遗产承受人, 受遗赠的人
Special usage:
residuary legatee
剩余遗产继承人
universal legatee
全财产继承人

a residuary legatee, clause, bequest
剩余遗产的承受人、 条款、 遗赠.
-- 汉英 - 翻译参考
(3) where a testamentary successor or legatee predeceases the testator;
（三）遗嘱继承人、受遗赠人先于遗嘱人死亡的；
-- law - 汉英
A legatee should, within two months from the time he learns of the legacy, make known whether he accepts it or disclaims it.
受遗赠人应当在知道受遗赠后两个月内，作出接受或者放弃受遗赠的表示。
-- law - 汉英
(1) where inheritance is disclaimed by a testamentary successor or the legacy is disclaimed by a legatee;
（一）遗嘱继承人放弃继承或者受遗赠人放弃受遗赠的；
-- law - 汉英
Article 21 Where there are obligations attached to testamentary succession or legacy, the successor or legatee shall perform them.
第二十一条 遗嘱继承或者遗赠附有义务的，继承人或者受遗赠人应当履行义务。
-- law - 汉英
Article 32 An estate which is left with neither a successor nor a legatee shall belong to the state or, where the decedent was a member of an organization under collective ownership before his or her death, to such an organization.
第三十二条 无人继承又无人受遗赠的遗产，归国家所有； 死者生前是集体所有制组织成员的，归所在集体所有制组织所有。
-- law - 汉英
"An estate which is left with neither a successor nor a legatee shall Belong to the state or, where the decedent was a member of an organization under collective ownership before his or her death, to such an organization."
无人继承又无人受遗赠的遗产,归国家所有;死者生前是集体所有制组织成员的,归所在集体所有制组织所有。
-- 英汉 - 翻译样例 - 法规
"A legatee should, within two months from the time he learns of the legacy, make known whether he accepts it or disclaims it. In the absence of such an indication within the specified period, he is deemed to have disclaimed the legacy."
受遗赠人应当在知道受遗赠后两个月内,作出接受或者放弃受遗赠的表示。到期没有表示的,视为放弃受遗赠。

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Note added at 4 jours (2009-08-09 15:01:30 GMT) Post-grading
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You are welcome. Good luck!