After doing more research, including manga reading. These are all of Alucard's abilities:
Alucard, like all vampires, requires blood to stay alive. However it is not shown in Hellsing as to wether what would happen if a vampire was not to drink blood. Seras Victoria tried to stay away from blood as much as possible during the first half of the manga and had no adverse effect whatsoever. Also, Alucard survivng 30 years without drinking blood can raise the speculations that Vampires do not require blood to survive but can be only be regarded as a craving. But it is still unclear whether Alucard survived because of his new found power.
Super Strength
Alucard can lift far in excess of 10 tons effortlessly. Upper limit unknown.
Super Speed
Alucard can move at teleportation-like speeds(faster than the speed of bullets).
Superhuman Reflexes
Alucard can catch objects moving at supersonic speeds with ease. He even caught Rip Van winkle's bullet(which traveled at Mach 3.5) and fought father Anderson multiple times to a standstill (both were moving faster than average vampires which usually dodges multiple machine gun fires).
Superhuman Accuracy
Alucard is very proficient in using guns. He has perfect aim and has taught Seras Victoria on how to shoot things more than a mile away without missing. He can also fire multiple bullets that does not miss without even looking.
Super Stamina
Alucard was never shown to tire and could continue fighting as long as he likes.
Immortality
Alucard does not age and as a vampire, he does not die. Also, he cannot be killed by any means necessary as he would only redirect the death to one of the souls he devoured. Father Anderson even said that the reason as to why Alucard can never be truly killed is because of all the souls he devoured. However, it is only a pseudo-immortality as he can probably be finally killed by destroying all the souls he released in Restraint Level 0 and by killing him.
Alucard also stated himself that he will not get weak to sunlight, he only dislikes it.
Invulnerability
Regular bullets, temperature extremes, bombs,etc. cannot harm Alucard to any degree. Despite his level of near invulnerability, Holy weapons can harm.
Healing Factor
Alucard can heal from any injury instantly without scarring including organs or missing limbs (when harmed by those who can match him in strength or holy weapons) If blown to bits he merely turns into a shadow and reforms.
Vision Powers
Alucard, like traditional vampires, possess enhanced sight, such as night vision (Alucard can see clearly in total darkness) and telescopic (can see events happening dozens of miles away as it happens).
Telepathy
Alucard can read the mind and communicate with anyone he so desires.
Telekinesis
Alucard can move objects with his mind. The upper limit of this power is unknown.
Invisibility
Alucard can turn invisible to the naked eye any time he so desires.
Intangibility
Alucard is capable of shifting his mass into another dimension, altering his density and thus allowing him to pass through any solid object, or allow solid objects to pass through him. This was shown when Alucard phased through a solid wall during the chapter where Seras Victoria was explaining that she was a vampire to the Wild Geese.
Shapeshifting
Alucard can turn into any form he chooses-from being able to turn different human beings to animals to even inanimate objects.
Shadow Manipulation
Alucard can turn into a shadowy form, which he can use however he wishes (turning into hellhounds,etc.).
Mind Control
Alucard has the ability to control the minds of any human, or vampire, he chooses (meaning he can control more than one mind simultaneously). The extent of this power is unknown.
Sleep Induction
Can cause someone to sleep by mere thought.
Hypnosis
Can send others into a dream-like state (both human and vampire).
Illusions
Can create false images in the minds of others (both human and vampire). As shown when he cast an illusion on Walter (making Alucard look like Luke Valentine).
Bloodsucking
Can absorb blood through his clothes or over large distances.
Memory Absorption
Can absorb memories through blood.
Soul Devouring
Owns the soul of whoever he kills.
Control Art: System Restriction Level 0
Alucard calls upon all the souls that he's devoured and summons them on the battle field to do as his bidding. The familiars that he has summoned have been stripped away of free will.
Omnipresence
When Alucard drank Schrodinger's blood, he had gained his powers. He can now also be everywhere and nowhere at the same time.
Combat Experience
Although Alucard prefers uses his vast supernatural powers to crush his opponents, Alucard has mastered all forms of armed and unarmed combat over his past life of 2,000 years.
Weapons:
The Jackal
A large black pistol made by Walter C. Donez, The weapon is 39 cm long and weighs in at 16 kg. It fires 13 mm amour piercing bullets that have a mercury core and is baptized in holy water and all this is encased in a silver melted down from a cross. and contains a spirit named "Willis" whom Alucard meets in a dream. It can also fire explosive rounds.
The Casull
This weapon is 29cm in length and carries 8 rounds, its weight is unknown, but it is said to be to heavy for a human. The Casull is Alucards first gun and as its name implies it fires explosive .454 Casull rounds that are encased with steel and in the center has silver melted down from a holy cross. It is often used in conjunction with the Jackal for maximum damage. Alucard only possesses of these, due to the fact that it often kills his opponent in the first few shots, much to Alucard's disdain(he prefers causing them a slow and painful death).
Source:
http://comicvine.gamespot.com/alucard/4005-44583/
With that, I say Alucard has a variety of tools and abilities at his disposal to find away to defeat Magneto. Perhaps he could distract Magneto with Hell Hounds or his Familiars long enough to get close to Magneto, phase through his shield and rid his heart out. Maybe Alucard could disguise himself as a shadow and once Magneto is in range, well you know the rest. Point his, Alucard would be extremely difficult for Magneto to dispatch, however, all Alucard needs is one opportunity to dispatch Magneto. Given that, I'm going with Alucard.
Vote Alucard.