In contrast to the stanza in <PERSON>'s chapter 24, in the Hákonarmál <PERSON> sends his valkyries to announce to king <PERSON> the Good that he has been granted a seat in the hall of the slain:
They spoke over his grave, as heathen people are used to do, and wished him in Valhal. <PERSON> composed a poem on the death of King <PERSON>, and on how well he was received in Valhal. The poem is called "Hakonarmal":
"In <PERSON>'s hall an empty place
Stands for a king of <PERSON>'s race;
'Go, my valkyries,' <PERSON> said,
'Go forth, my angels of the dead,
<PERSON> and <PERSON>, to the plain
Drenched with the battle's bloody rain,
And to the dying Hakon tell,
Here in Valhal shall he dwell.'
Source: Wikisource contributors, 'Heimskringla/Hakon the Good's Saga', Wikisource , 13 April 2012, 18:55 UTC, https://en.wikisource.org/w/index.php?title=Heimskringla/Hakon_the_Good%27s_Saga&oldid=3740623 [accessed 22 June 2015]
Thus <PERSON> appears to be in full control of who enters Valhalla. However, even if that's not the case and <PERSON> does get first pick "of the slain", it doesn't really matter. All of the fallen, including those who end up in Folkvang, are chosen by <PERSON>, as <PERSON> - through his valkyries - chooses who lives and who dies:
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There are still others who are to serve in Valhal, bear the drink around, wait upon the table and pass the ale-horns. Thus they are named in Grimner's Lay:
Hrist and Mist
I want my horn to bring to me;
<PERSON> and <PERSON>,
<PERSON> and <PERSON>,
<PERSON> and <PERSON>,
Gol and <PERSON>,
<PERSON> and <PERSON>,
And <PERSON>;
These bear ale to the einherjes.
These are called valkyries. <PERSON> sends them to all battles, where they choose those who are to be slain, and rule over the victory. <PERSON> and <PERSON>, and the youngest norn, <PERSON>, always ride to sway the battle and choose the slain. <PERSON>, the mother of <PERSON>, and <PERSON>, Vale's mother, are numbered among the goddesses. valky
Source: Wikisource contributors, 'Prose Edda/Gylfaginning', Wikisource , 29 January 2013, 01:25 UTC, https://en.wikisource.org/w/index.php?title=Prose_Edda/Gylfaginning&oldid=4271175 [accessed 22 June 2015] 351